I would try to beat them and rub it in their face. But if that's not your cup of tea, disabling the chat will do the trick.
How to deal with rude people
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My chat is disabled so I can concentrate on my game. . . . 
Dec 19, 2020
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#24
Rudeness is one thing, and sometimes you need to develop some tough skin to deflect it. but there is a point at which rudeness crosses the line into aggressive, threatening, and bullying. Report it right away, and block the person. Disable chat until you feel ready to do otherwise. Also, you’ll find out over time that probably 95% of the people you play will be good people with good sportsmanship. I had a very early experience with a rude jerk too. But I moved on and learned that playing people from all over the world was quite enjoyable, even if they did beat me again and again. 
First and foremost, protect yourself, and always let your parents know when this type of stuff happens. It sounds like you already do, so keep everything transparent (no pun intended), they can help you navigate the few bad players and their sophomoric behavior. Enjoy the journey friend!
Dec 19, 2020
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#25
what I do is I get as
SALTY, CONFUSING, AND PASSIVE-AGRESSIVE as I can. They get thouroughly confused, maybe talk some more trash talk, but eventually they will give up. In other words, play dumb, act like their dumb until you convince them. Such as...
You are playing a game you lost your bishop.
Them: Ha ha you are such a patzer etc etc.
You: What do you mean?
Them: You hung your bishop
You: What bishop?
Them: What do you mean it was played 2 moves ago.
You: You mean 4 moves ago?
Them: Well... 4 half-moves ago but 2 moves ago. Don't you know chess???
You: So I was right. Stop being so strange.
Note: you are not being rude, just Salty, Confusing, and Passive-Agressive. Eventually, the don't want to talk to you, and you win!
Dec 19, 2020
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#27
That's why I mute/disable the chat. If they still really want to talk trash they will have to take the time to DM me and be pathetic. I come to play Chess not trash talk.
Dec 19, 2020
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#28
do all of you turn chat off? But sometimes its nice to talk to your opponent to discuss moves or ideas. Sometimes i like to tell my opponent they played well
Dec 19, 2020
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#29
I leave the chat enabled. If I get a jerk, I then disable it for the game. What are you doing?
Dec 19, 2020
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#30
I am the opposite I say horrible things to myself dude and edge on the opponent to say bad things as well because I am bad at chess man I am just horrible at chess and I want them to know so I trash all of my moves in the chat because all of the people I play are 100x better than me and I somehow draw out of luck
Dec 19, 2020
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#31
And if you don’t believe me look at my game vs CraiceK he was way better than me and I trashed myself in the chat constantly which is why my time was so low and then we drawed but if we didn’t I would have blundered queen probably
Dec 19, 2020
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#32
So the best way to handle haters against yourself is be a hater against yourself even though CairceK wasn’t a hater he was pretty good
Best thing to do is to turn of the chat. I think it’s quite sad that there are a few people who want to be negative.
This guy was so mad at me when I won his rook. The best thing to do is stay calm and report him/her. This game is currently happening right now. He/She has been reported by me. Thanks for creating this forum.
Actually, I enjoy it. I had a rude player who insulted me, yet with two queens he lost on time and called me a "clown"! What does it make him loosing to a clown?