Threatening violence, actual tossing of cards or chips in a physical manner, talking during a big decision in a hand they are not involved in.
I never say much - but I had a confrontation with a gentleman last winter before covid kicked in playing 1/2 live and I called a 4 bet all in from him while I had KK and he got pretty upset at me for calling because he moved in with J6o and his reasoning was "how don't you figure i have AA there? I don't get how you make that call, it makes no sense" - my response was "if you expect me to fold the 2nd nuts preflop maybe you are playing the wrong game bud" - while he didn't threaten me or try to physically fight me - he did continue to swear and rant for a good bit upset that I made the call and he was forced to table a bad hand and lost over $400 as well.
The point is some ppl are just a-holes, some ppl are easily offended, and others are just controversial and feed off of negative energy. I wouldn't concern myself with certain things but when ppl start becoming obnoxious and physically violent then its time to call the floor in.