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

Murder him, simply murder him. No muss no fuss.

As an E6 reserve going on temporary duty in an active unit, i assigned tasks for the day and had that smart mouthed E3 stand fast. Then had a soldier to soldier talk with him. Next day the PT test came about and he knew he was screwed!.

As an NCO and then as an Officer I made my policy public knowledge. "If you challenge me or dis respect me in public, I will rip your face off in public" Not the best policy but very effective.

Pull him out of formation and turn him over to my CSM

Key Part of Example: They blatantly complain and tell you to choose someone else. You calmly tell them they will do this task and they tell you to shove it and give it to someone else.

Summary of the Elements of Article 91: The government may accuse you under article 91 for striking, disobeying or using contemptuous language or disrespect toward a warrant officer, noncommissioned officer, or petty officer of the U.S. armed forces.

At a minimum Counseling, but could just refer to Article 15. Given the gist of the example probably start with a Summarized if the soldier is salvageable or a Company Grade.

You immediately lock everyone's heels. Have Seaman Nobody fall out and place him at the front of the crew facing them. Tell the crew Seaman Nobody believes he is better than the rest of the crew and he will be given two choices. Tell Seaman Nobody that if he fails to accept the assignment he will go on report and face Mast. I'd dismiss the crew to their assignments. Now Seaman Nobody has a choice; 1) report to his assignment or 2) Place him on report. The OinC would give him two choices 1) accept Mast (fine, EMI, restriction) or 2) Go on report to the CO, which could result in a Courts Martial. If he accepts number 1 the crew sees that he has given in and is doing what he is ordered to do. If on the other hand he chooses 2 he goes on report and the crew will know it. Either way you stop the infection. Now if he chooses 1 at Mast the crew sees the punishment for being a wise ass, and if he chooses 2 at Mast the crew knows he's doing time in the Brig.

WOW! First, finish giving assignments and have the PV2 (or SA?) stand fast! Then counsel him on what a Lawful Order is and ascertain if he has any questions. Do it firmly, but calmly. If he gives you ANY crap, take him to the Orderly Room and have him sit while you confer with your supervisor with the intent of (at least) issuing a WRITTEN Counselling Statement. The statement needs to address his insubordination, overall attitude and disrespect.
Any problems after that, he's toast. It is crucially important to keep your cool - firm, but level headed and fair. I called it, "Giving him rope enough to hang himself;" but with the hope that he wakes up to the fact that he's subject to discipline if he continues his stupidity.

I once had a company commander,who,when I first reported to him as part of my newbie welcome,Returned my salute with the following remark,My name is XXX , I am a Capt in the United States Army,I maketh and I taketh away.The first one is on me all the rest are on you.Do you have any Questions PVT. I learned that using that system was a pretty good way to get the job done.A good leader simply must be aware of what the people under him are going through.And if the person is simply being an axxhole then make an example of him/her. Even if there problems at home,get the offender the help they need but make that the offence is corrected.At least,thats the way I see it.

Pull him/her asside after formation and counsel them and start a paper trail for futer disciplinary purposes...

PT until total muscle failure. He’ll learn quickly.