This is, of course, a shame. I've only had a deceased service member one time (ANC>MSP) and we all stayed seated and several of us cried.
I find it hard to believe the whole plane would do it intentionally. I have to wonder how well the overhead speakers work and if everyone heard. I don't hear a lot of what they say on planes and I'm trying to listen. I really hope and think most people wouldn't be intentionally disrespectful.