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

Have him stand fast after formation falls out, and get his story, verbal reprimand, or written if necessary and forward information up the chain if required.

Coming from a Military School that made basic training in the Navy seem like child's play. I would inform the entire unit that due to one of it's members lack of military etiquette they would be drilling and running the next two days. If bye chance after said drilling and running they could pull together as a unit. There would be know need for any further enlightenment. Let the unit take care of it's own theology.

Depends on how jacked up the E5 was the other few months. You can't beat a deadhorse and expect a race horse

As a former FMF DOC I had this happen to me by a new Marine fresh out of boot. I gave him an order and I believe his response was " I don't take orders from a squid." Being taken back by the response I received for a brief moment, I paused before I told him to drop, and before I even had the chance to educate this young Devil Dog my Gunny just so happened to be walking up behind this youngster and snatched him up by his collar and made it crystal clear to this young Marine that he would never question an order from an NCO, and if he ever heard of him calling his DOC a squid again that he would take him to the wood shed. After the youngster was done being educated by my Gunny. He was excused, very tired and sweaty. My Gunny then turned to me and said. " DOC, if you ever hesitate to put another junior Marine in his place, I'll ensure you will feel more pain than all of that motrin stuff in the world won't be able to fix you". Needless to say, I never had a problem with a junior Marine or any other junior again.
That being said, it was a different time, but I still feel that the military should not change. Those moments of getting smoked, taken to the wood shed etc... Is what built character, and it ensured that all orders were followed without question or hesitation. So if in today's military orders are able to be questioned or blatantly disobeyed then it would create a disastrous result. So may answer to the question is simple.. Smoke that junior Soldier, Sailor, Marine or Airman. No questions, no hesitation. Period.

Brat ur face soldier

Hmmm..... My army career started at the ripe age of 7 yrs old when my dad enlisted. I quickly adapted to his "new style" of parenting that consisted of him controlling what was most important to me.... MY PERSONAL TIME!! Ass whoopins became ineffective to me by the age of 10 or 11. By the time I was 17 he was a SFC-E7. I was feeling kinda of froggy one day because I was tired of his treatment because "I was almost a man". Some how, I fixed my mouth to say the words 'NO"!!! And when I woke up....... I remember him telling me why he did it and if I did not respect him in "his house" I would not learn to respect others or myself in the future. Therefore, no one would ever have respect for me. Then he asked me what my problem was. 2 yrs later at the age of 19 I enlisted and it all became clear to me. Think before you do because there my be a problem with an individual personally and as leaders we need to get to the root of it. Also, when we pin that rank on some of us believe that it comes with superhuman strength. It does not. We don't hear about it much but I have witnessed a "dickhead" NCO get his ass kicked on a few occasions way before we started considering these new soldiers "bad apples". I stopped hollering and screaming my last 7 yrs of my career and I did my duty with a pen and readymade counselings. Less stress on me and a better understanding for each other. That was the best angle for me. Put a smile on your face while your doing it too. They hate that. LOL

Speak when spoken to

I LOUDLY tell them that they signed up to be soldier and that orders are to be obeyed. There are plenty of way to punish a 'cruit who refuses to do what is necessary.

Take him to the woods at gun point and make him dig his own grave!

I would tell him just start pushing
Because it know room for defiance in any branch of the military.
Because we all know every thing we do in the military is to train for a bigger task
If he didn't think it was right he should had use tack and pull him a side and told him why he did not think he should have to do it
You don't have we respect person but do have to respect the rank ask long as he out rank he he have to listen to him and if you don't think it right go to some one higher then him. That y we have a Chang of command