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

Yes you should…immediately!

If you are in uniform and on post, yes, he should know better.

Depends on what you want him to think of you.

You check them on the spot. Not a friendly reminder but like you grabbed him by the stacking swivels . T. D. Rice HMCS USN Ret.

I'm an old AF SAC guy. We lived, trained, survived and got fired by strict standards. BL: You're an officer. If the troop has seen you in uniform...s/he knows who you are. Not enforcing the standards means you accept a new and possibly lower standard. You can quietly, respectfully, w/out embarrassing anyone fix this immediately.

YES!!!
I was an E-4 when I got out in 1992. While I was in, I was part of a group that worked with the base chaplain. He was an easygoing & friendly guy. One time I was on post in uniform walking & saw him likewise out in uniform. He was with with another officer. I lost my track for a moment & started to approach him in a friendly manner & was sticking my hand out to shake his hand. I IMMEDIATELY saw the reaction of the other office & self-corrected for a standard salute with greeting. Later on I apologized to him about it. It never happened again when I saw him out. He didn't seem too upset about it, but I was embarrassed & apologized repeatedly.

You should correct him politely. There's no reason to go full DS on him, but say "Good morning, how are you today? I don't want to come off as crass but I'm uncomfortable with this level of familiarity between us. Please refer to me by Sir or Rank/Last Name. Thanks for understanding."

Resign your commission if you don't know the answer. And do you not have a good NCO you trust to ask a question like this?

I would reply something like, Spec 4, how may I help you? If concept didn'( connect, go from there.

I would. That is very disrespectful if he knew you were an officer. You don’t have to scream or threaten disciplinary action. Just explain why his action was inappropriate