When an E-4 calls me "hey" or "hey man" knowing that I am an officer, should I bother to correct him?

EXACTLY! Well stated.

Yes. This.

MAJ (Join to see) what I’m saying Is a counseling with his NCO leadership to recalibrate his customs and courtesies module. Where did you get UCMJ out of that? OP was asking about on the spot correction, which I’m assuming has not been attempted since he’s asking if he should or not. You walk be something ate up, you just set a new standard.

That makes sense. Your initial response didn't reflect your second post, though. Total agreement: the Soldier requires some mentorship where, apparently, some might be lacking. What does "walk be something ate up" mean?

MAJ (Join to see) when you walk by something ate up (not right) and you do nothing you just let them know it’s ok…setting a new standard

That's right, LTC Friendly, some of our "standards" are stupid. Please stop blindly following orders, question them for their validity, and do something about it. Some of our standards are there for a reason; others aren't, they're just stupid. Wearing headgear, while in a convertible … stupid. Army OCS as nothing but hazing ... stupid.
Granted, the further from the flagpole, the better it gets. The further from morons. It's true: the first time I ever told a LTC to go f**k himself, he tried to lecture me on my ballistic sunglasses. Yes sir. He didn't even have a combat patch.
Have some guts and figure things out yourself. Gee whiz.

GySgt (Join to see) - I agree with you, to a point, as my senior leadership addressed me by first name when I worked in Engineering and, later, in Intel. In Engineering, we used first names when working closely in the shop (these were all company grade officers, and it is an Air Force custom dating back to at least WWII). Proper protocol was observed when any outsider was present, regardless of the outsider's rank. When I was in Intel, I still called them Sir/Ma'am, or by rank, especially MajGen "Kip" Clark, who I have known since he was a LtCol. I considered it an honor when my leaders trusted me enough to call me by my first name. Having worked with the Marines (a group that I have great respect for), I understand the cultural context of your point of view, and I would address you as Gunnery Sergeant until told otherwise, and I would address an E6 as Staff Sergeant until told otherwise also, even though we are the same rank. However, the Army and the Air Force are slightly more relaxed in how the enlisted address each other (If was talking to a Master Sergeant, we would address each other as "Sergeant") That's why I think you were wrong to down vote the OP. We can disagree without being aggressive about it.

TSgt Carl Johnson - Thanks for the response! And your logic is sound. Yeah, the Corps was and maybe is still pretty uptight about customs, courtesies, and what would be considered too cozy of relations. Suffice it that some of those officers are now my friends (I retired in 99) and we're on a first name basis now. Now I'm pretty undisciplined and would likely get in trouble in the Corps. LOL

Officers are never subordinate to NCOs. I read that in a manual once.

MAJ (Join to see) Sir,
Before an Officer (2LT and 1LT) becomes an EOD Team Leader Certified they run as a Team Member under a senior Team Leader (E-6 sometimes an E-5)). There they learn about conducting the EOD mission. While on that team they still have their general military authority but they do not have the positional authority they take guidance and orders from the EOD Team Leader who is responsible for the mission as the LT does not possess the skills and experience to run the mission. When the mission is over things go back to normal.

SSgt Joseph Baptist - As I said, we are operating on different premises. I don't have a problem with your response. It matches your premise. But I don't feel any different about my response. It matches my premise.

In my premise, the soldier knows the officer is an officer. I'm not putting it down to a nefarious plot. I'm putting it down to some junior enlisted personnel think that there is a difference between military courtesies "off-duty" and "on-duty." As a junior officer, I probably had a handful of incidents where junior Marines thought all that "sir" stuff didn't apply out in town. They thought it was just for boot camp and school of infantry. In the Marine Corps it applies all of the time.

Marines are probably the most formal of the services. If I saw a Marine in town, we're both in civvies, I recognize him or her, but have no idea, rank or name; I'd render a courteous greeting: "Good Morning", etc. But "Hey," "Hey man," "dude" etc. IMO such greetings assumes a level of familiarity with someone you don't know. I don't assume familiarity with people I don't know.

If it is just a case unknowing recognition "Common courtesy dictates that you give some sort of greeting or acknowledgement to someone you recognize, even if you vaguely recognize them." Then it doesn't pass the "obnoxious" bar of which I spoke. If I don't respond to "Hey man," The SPC is free to think I'm a stuck up ass. We are never going to be drinking buddies. His opinion of my personality is irrelevant. There is no confrontation. Both go on about their business. If the SPC is trying to make a contact that extends beyond a casual acknowledgement, obviously the context of the circumstances matters. But it may also indicate that he does recognize the officer and is disregarding military courtesy.

If the officer believes that the SPC does know the officer is an officer, once again there is no confrontation unless the SPC pushes it. The officer addresses it with an appropriate NCO/SNCO. The NCO/SNCO is then free to ask the SPC if it was a knowing or unknowing error. The NCO/SNCO, based on his assessment can decide whether a "word to the wise" is all it takes, or the SPC needs to be "tightened up" a bit. As I said before, generally Marine Officers don't get involved in matters of correction when it comes to customs and courtesies. They refer it to the appropriate NCO/SNCO.

The officer doesn't need to put on his "ugly suit," unless he knows the SPC has been advised by an NCO/SNCO, and doesn't care to change the behavior.

Maj John Bell - Sir, you are 100% correct with your premise, as is @SSgt Joseph Baptist with his. I saw it from both of your perspectives, more or less, but attributed the SPC's casual, "Hey man," as ... uhmmmm, youthful ignorance. IF the Sarge's perspective is correct, he's right; likewise if your perspective is correct, then you are.
Would have been easier had the 1LT mentioned whether they typically worked together or were just in the same unit which could be Company, or larger sized. A lot of possible variables there.
ALSO, and this is NOT a jab at either the Corps or the Army (or USAF as SSGT Baptist is), but different branches have different approaches to such situations. Marines go to the service member's NCO to address such things, while other branch's officers tend to deal with it more directly. Both systems work - the Corp's is MUCH more ... what? Structured with more acute discipline tactics, and there's nothing wrong with that - "IT's THE CORPS!" :) LOL

SSgt Joseph Baptist - In the Army, it does not matter whether you are on or off duty because you are always on duty subject to muster. I was in a combat unit and my NCOs and officers would definitely not have tolerated that casualness. As Major Bell stated, NCOs are responsible for making those corrections. Tolerating that kind of insubordination is not good order and discipline. The post mentioned that the service member had rendered the proper respect in uniform. If I have worked with an officer more than a few times, I would have recognized him/ her off post. Maj John Bell

Yes. This. All day long. Thank you.

Do we really need to explain this to you? A LT, in civilian clothes, encounters an enlisted Soldier outside of normal duty: the Soldier addresses the LT bereft of his commission. The LT, thusly confused, posted his question on this forum on 1. If his initial response was correct and, 2. Requesting guidance from forum members like you.
How would you "correct" the E4? Lock him up? Make him do push ups?
I would love to hear how you would correct him, if you had a commission, and an enlisted member of the military disrespected you in public, out of uniform.
Think of it as a thought experiment.
Standing by.

Do we really need to explain this to you? He asked if he should, not how he should. However, since you’re "standing by", the SPC knew he was a commissioned officer as they’ve crossed paths in a professional environment and the SPC addressed him as “Sir”.

How I would address this is one of two ways, I could make an on the spot correction, if I believed the situation warranted one. If I didn’t, I would wait until the next duty day, pull the SPC to the side, and remind him military customs and courtesies are not just for “while in uniform”.

No I wouldn’t “lock him up” or make him do push-ups. Not tools I generally went to for “corrective action”. A professional Soldier to Soldier talk is a much better tool. “Locking them up” has its place. I don’t see this situation as one, unless the SPC decided to get belligerent while being corrected. Push-ups don’t teach anyone anything. It’s the tool of the lazy leader.

Since you actually don't need a commission to correct an enlisted Soldier for disrespecting you in public, out of uniform, it’s no different than how I would have dealt with it as a NCO and a Soldier addressed me as bud, dude, man, or anything else just because we were in public and out of uniform. MAJ (Join to see)

Now THAT is a great answer! No sarcasm, seriously.

Well, You did get a laugh out of Me on that one. LOL

Man, I hated that.

That is what I expect from my leadership. It is not about the individual. It is about keeping up military traditions. Thank you! LtCol Robert Quinter

Yes, sir. Totally agree. But "gain" a commission? I like to think I earned mine. And the first time as an Army Staff Sergeant I said "Yep" and "Nope" to a Marine Lt. Col. was the last! That was a dressing down I will not forget. Deserved every single word. SF

Your sentence makes no sense. Should have ... already ... what are you trying to say?

what is meant, I belive, is the correction should have been made the 1st time it was said. We in the Military, both active, reserve, ng, and retired are professionals. We have a reputation to uphold both while actively preforming our service (on duty) and after hours (off duty/retired). "Hey" or "Hey Man" is not an acceptable address at anytime, especially not among Professionals. (some folks just need to read Miss Manners!!)

What's the correction which needs to be corrected? Is it UCMJ 89?

Elements

That the accused did or omitted certain acts or used certain language to or concerning a certain commissioned officer;
That such behavior or language was directed toward that officer;
That the officer toward whom the acts, omissions, or words were directed was the superior commissioned officer of the accused;
That the accused then knew that the commissioned officer toward whom the acts, omissions, or words were directed was the accused’s superior commissioned officer;
That the under the circumstances, the behavior or language was disrespectful to that commissioned officer [1].

Maybe you're right. But be very careful when you start quoting regs. There are other articles.

I didn’t quote regs. You did.
Anyway, I think UCMJ would be unwarranted. A simple, “hey soldier, you’re not my friend, brother or boyfriend. When interacting, even if out of uniform, please refer to me as sir” would just about cover it.

But if you’re good with soldiers running around, calling officers bro, fella, guy or anything else, more power to you. Again, the Army only gets soldiers that its leaders produce.

SGT (Join to see) did we all just totally skip over the "outside of work" part.
He's lucky he even got acknowledged.

In some areas, MP's work fairly closely with CID. We were always, ALWAYS taught that when you encounter an Agent (or even MPI) in civilian clothes, to NOT address him/her, until and only IF, they speak to you to let you know they're not working.
In today's realm of potential dangers, perhaps the, "Hey man," OFF base might be what the SPC thought was an appropriate recogntion; but without tipping anyone that it was a miltiary officer he was greeting. "Could be."

Did the OP say he was an MP or working with CID, and the whole "Yeah?" phone number thing? Did I miss something? Or are you just trying to tell your own story?