Am I alone in finding this extremely rude?

No, that's the me generation/millenials for ya though. Nobody matters but themselves.

All 'bad behaviours' are acceptable in moderation.

Nonsense. Being a little obnoxious is still being abnoxious.

I don't think there's anything that can be done about it...

Nonsense. Call them on it & Tell them to knock it off as loudly as necessary.