How would you react if you were on a flight where a family was boo'd for being allowed off the plane first to receive their soldier's body?

I'm responsible for my behavior, not theirs. Lead by example; stand and/or show the appropriate respect and let their ignorant, boorish behavior reflect on them in contrast.

Would it have made a difference if the passenger had sat in the cheap seats with you? But since you asked, once booed is freedom of expression, twice booed is stupidity.

I would feel sick and realize how non-empathetic ppl can be

Professionalism. Stand to attention, salute the casket if visible. Sinking lower by throwing your own tantrum and slinging insults and profanities at hecklers reflects less honorably on the uniform and principles than the hecklers themselves. Be a man, not an emo teenager. We are supposed to be better than that- experts and professionals at all times. Playing the pathetic tribalism game helps VALIDATE and LEGITIMIZE the disrespect that started the situation. In fact, trying to provoke and film such a display may have even been the motivation.

Well, I am old with mobile issues and cannot defend myself well, never mind others. but I would not be surprised in today's America. Most certainly I would wish worse on those that would boo.
I am glad I no longer can be asked to sacrifice for these bastards.
Today it is," Know the real enemy, for they walk amongst you "

It boils down to complete lack of respect. Any reply would be futile since it would incur more disrespect directed towards you. From a personal point of view, I would like to put them on the front lines of any fighting and watch the outcome.

This sounds like a trolling post to stir a reaction. I don’t really believe that there is someone stupid enough to do what you are suggesting.

I would stand and salute the family making sure all those who booed seen me and my eyes. Thank them for their soldier and give my condolences.

Trip and flail my elbow?

I doubt I'd be the only one to stand up and eye fuck them.