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?

Shut him the f up.

Depending on circumstances I might just call them out for being a disgusting, disrespectful, pos. Then again if it were a male and he caught me on the wrong day, I might have jerked him to his feet and told him face to face of my displeasure at his disrespectful attitude...

Give the opportunity... I would silently step in front of said individual...either face to face, or with my back to them, to provide buffer for the escort and family members. If they were in the aisle, I would “assist” then in finding their seat again.

I would be a very unhappy camper. The we the American people owe the gold star families everything.

"I see you're ready to sign up to take that young man's place; the recruiter will meet you in the jetway..."

Stand and salute, give the family time to leave the aircraft, then put the assholes on the spot, there will be no disrespect, period, either stand and give the family your attention, or sit and shut your nasty mouth

I was in uniform, had no idea we had a fallen on the plane. One of the flight attendants quietly asked me if I had known and asked if I'd talk with the pilot (who was AirNG), we talked about details and that he was the in Afghanistan coming home to a single mom who was waiting at the small airport in WI. I agreed to do everything that needed to happen in order for the mom to receive her son. I asked where the escort went and was told he was too drunk to perform the duties. Yes, passengers gasped when the pilot got on the intercom and made the announcement, but honestly, there's no reason to even engage with that fucktard.. maybe a nice throat punch as you walk by though.

"If you don't want to be stuck on this plane for HOURS while they call the cops to handle the incident I'm about to cause, shut your mouths and show some damn respect."

Tell everyone to shut up and get out of the families way

I certainly would educate him on the supreme sacrifice that the deceased had made in order to protect his/her right to express that "Boo". I would then tell them how extremely callous it was to do so and ask him/her how they would feel if it happened to be them in that situation. The family deserves respect and the person's abject failure to show respect is shameful.