Have encountered a couple. I just try to ignore them, but the Internet sadly makes this a thing.
Chess Bully

I just disable in-game chats. It is a lot less stressful and distracting. I think people do it on purpose to get a psychological advantage.

So I was playing a 3/2 bullet game. Of course, as soon as I start playing my son texts me. I got distracted and made a bad move.
But then the opponent starts chatting, talking about how he cant believe I made such a dumb move and that learning the "Queens Gambit" is the most fundamental thing in Chess.
So I replied - and told him he was being a Chess bully.
He genuinely seemed to think that he was not being a bully and was "helping me learn" by telling me how stupid I was to miss his attack.
Over the years, I have not encountered such Chess bullying very often - but maybe it is more common than I thought?
I tried to explain that it was similar to being bullied in school but I dont think they cared.
TLDR; Dont be a Chess Bully
Disable the chat. Those are losers, and they feel better when they first get a win. Just next and keep playing

I just disable in-game chats. It is a lot less stressful and distracting. I think people do it on purpose to get a psychological advantage.
I disabled in-game chat too, on day one as a member here. A guy kept saying things like... "Are you brain-dead - RESIGN NOW!" ... when I was 3 pawns up!
I enjoyed winning the game, but I figure there is no point in poisoning my eyeballs with negative tripe like that on a daily basis. 😵💫
So I was playing a 3/2 bullet game. Of course, as soon as I start playing my son texts me. I got distracted and made a bad move.
But then the opponent starts chatting, talking about how he cant believe I made such a dumb move and that learning the "Queens Gambit" is the most fundamental thing in Chess.
So I replied - and told him he was being a Chess bully.
He genuinely seemed to think that he was not being a bully and was "helping me learn" by telling me how stupid I was to miss his attack.
Over the years, I have not encountered such Chess bullying very often - but maybe it is more common than I thought?
I tried to explain that it was similar to being bullied in school but I dont think they cared.
TLDR; Dont be a Chess Bully