How would you react to an E2 who "smart mouths" you in formation?

Wall-to-wall counseling is appropriate, yet can backfire in intended outcome. Best is to talk with the young butterfly wings alone to understand how he feels and thinks, because some privates erroneously assume that their smart ass attitude will help them be noticed. It is our responsibility as leaders to assure the butterflies that they are an integral part of our animal kingdom and that their achievements will speak louder than their words or inappropriate behavior. If the private accepts this verbal counseling as guidance to succeed then, no further action will be needed. However, if the matter continues then, make the verbal counseling a written warning that such inappropriate behavior will result in UCMJ action. I personally doubt the matter will be treated without need of written counseling. I believe in process and, not jump to any extreme on the outset.

Our E2 in question is in serious need of correction and I would not hesitate to do the correction, sadly I then would be in trouble!! When I was an E2 there was no leeway in regards to following an order, you either complied or you received an Article 15 and probably booted out of the Army!

Start a paper trail. First time a verbal warning as the pattern hasn't been set yet. Second time a letter of counseling in this individual's file. Third time brings action through the first sergeant, fourth time from squadron commander. If it goes past the squadron level that individual's career will be VERY short.

Time to get in his face and let him know in no uncertain terms that he was given an order and he will comply period and now. Anymore back talk and we start with him getting an AR-15, restricted to barracks, extra duty and lose of some money AND HE WILL Follow orders I gave him NOW.

Read the room. Sometimes it's a chance to build relationships with your formation. If not...making everyone else in formation push while he stands there chillin is always a good way for the herd to fix their own.

You need to establish your authority, given to you, by your rank and position. If a New Troop/Sailor/Marine/Airman/ Space cadet.. whatever, you need to stop that behavior at once. If being polite / respectful will not work, then adjust your leadership style.
If that individual Tells you to "shove it" .. you need to destroy that individual. Through either Corrective training/ Administrative Actions/ or any other means you have t your disposal.

Also if you are unable or unwilling to perform as a Leader, then maybe some self reflection is needed. Ask yourself.. Do you have what it takes to LEAD? If Yes, then what do you need to do to step up. If the answer is NO, then admit it , and remove yourself from that Leadership position

This is tough, back in 1975 or so you’d be privately disciplined, but in this day that would be a career ender. First thing is the company Gunny needs to know your dealing with a shithead, and you need his advice and support. I’d take his entire squad and continue to give them the shittiest of details, I’d make them suffer as a group and let them correct the Private’s attitude. It is a team game after all and your only as strong as your weakest link. I’d firmly explain that to them and have them thank Private Shithead. I might even article 15 him on a second in fracture, and I’d take his stripe, his money and restrict him to quarters. This is the kind of problem guy, that doesn’t carry enough water on a ruck because it’s heavy, his rifle looks like shit as would his magazines. He probably falls out of runs and is in general a slacker. If it gets to a 15, the Company Gunny takes over making him miserable to the best of his ability. If he’s still a problem you muster his ass out and send him home with a General. There’s no time to suffer fools, be gone.

I had a similar experience. I first ask, then demand and finally had to give a Direct Lawful Order. The Soldier still refused to do the task. So I proceeded to file charges against the individual for Disobeying a Lawful Order. I forget the UCMJ Article but after I filed the charges the individual ran to the 1st SGT who inturned drop the charges. I don't know what to took place between the individual, 1st SGT and the Commander to this day and it's been 24 years ago. So I went and submitted my retirement papers and retired. If I wasn't retireable yet, I would have requested a transfer. Nothing but a little snot nose twrap still tied to his mother's apron strings. I'm done and no time for this garbage. In your case you have an extra charge as well. Being disrespectful. PO1 George Martin! Get the manual on Court Martials. They are service specificate. https://en.wikipedia.org/wiki/Manual_for_Courts-Martial

Maybe it was a brain fart that just occurred, dismissing the squad, you pull the young man out of formation, you have him follow you away from any one watching or listening and have a few choice words, find out why the outburst and go from, it could be bad news from home, a girlfriend, could be something so small that this person was in over his head, and took it out on you, not knowing what just took place and have him apologize and give him a stern warning not to do it again, next time it won't be a stern warning, but could go on his military file, give the guy a break and watch him closely, keep tabs on that person you never know what's bothering him

I stopped reading at the second sentence “You’re a senior E5”. WTH does that mean? You got passed over on the E6 board or never got recommend? A Command Buck Sergeant CBS?