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

First thing to do is get very quiet. This forces every one to listen closely, and more often gets better attention than shouting does. You ask the soldier if he remembers taking his oath, wherein he swore to follow the orders of the officers appointed over him? You remind him that he is an E-2 under your command a non-commissioned officer, and if he can't understand that or follow your lawful orders, you will be glad to march him down to the First Sergeant, where we can start proceedings for a General Courts Martial.

I did that exactly once with a troublesome troop. He called my bluff, then found out I wasn't bluffing. I marched the soldier down to the orderly room (after finishing the other assignments first) and told top to start paperwork for a an Article 15, that this barracks lawyer would then likely request and require a General court. Top gave out a low whistle and asked the Private if he understood his oath. The soldier said he did, but looked confused. The first shirt told his clerk to get the article ready, and then the soldier asked if there was a way out. I said at this point the only way of of the Article was requiring a General Court. He did, and found himself out of the army a few months later.

I never had another problem again, as word had gotten around.

An even better question yet. Your an E3, (yeah I wasn't always the best of soldiers) and your the range master, for a long range shooting class. But an officer (a major) don't like that thought, and asks, "Why do I have to listen to him, he's just a PFC?"
My company commander, (a captain) handled it wee in my opinion. He asked the major straight out, "Sir, can you hit a man size target, at 1,000 meters?" The major's reply, "No on can do that." The captain, "All do respect sir, he can and that is why HE is your range master today." There were no other questions.
As to the E2 not wanting to do his assignment, extra duty, CCF, and article 15, OR IN MY DAY OF BASIC TRAINING, the drill instructor and the E 2, step into the bathroom for a bit more serious discussion.

Kick his maggot ass.....

"You will follow orders or you will be short of cash next payday. You choose."

If I am not mistaken, an individual that shows themself to have a personality inconsistant with military service, may be summarily discharged without gaining any advantages for their service. If I were your company commander, they would have been on the "first thing smokin" out.

It would be all bad... That's UNACCEPTABLE!

Take the young Pfc aside and explain he does not have the right to refuse orders .. He will either comply or face Punishment under Article 15 UCMJ.. Conduct continues separate from Military.. Do not pass them along and make some one else put him out..My unit we had 2 types of Troops those that we were keeping in and those we were putting out!

Up against me back in the day? Your my dog! We are going to play games my way! Full ruck at 50 pounds, lbe, helmet! You are two steps to the left, two steps back. If I stop you immediately go to parade rest, if I turn around you go to position of attention immediately and drop to the front leaning rest and commence 20 push-ups, you will do this for a solid week! At night you are restricted to barracks, this will continue into the weekend which is now mine. I will volunteer you for 1SG detail during the extent of the weekend. Failure to follow my orders will result in a summary article 15. Bet your last dollar I would pursue it! I will have discipline in my ranks and make an example of you to the others. I actually did this with the blessings of Top and the CSM. He made the mistake of complaining to them. After they found out about his insubordination they wanted a piece of him. I don't know how they do it now but back in the day we didn't play. Running your mouth had severe consequences.

Disobeying an order, disrespect to a senior NCO Article 15. Tighten all the sphincters simultaneously.

"Sometimes people are defiant because something happened and they feel out of control so they try to take it wherever they can no matter how inappropriate. Sometimes a wife cheated or a parent died. Sometimes the hospital calls and congratulates you on having cancer" Really??? How about they are defiant because someone is shooting at them in combat or their buddy was just blown to pieces? Don't you think the whole purpose of unquestionable compliance to any lawful order is to make the Marine follow that order in spite of the horrible circumstances he/she is confronted with? When the mission is to take the beach, no one cares if you've had a bad day, the only thing that matters is that you complete your mission.