First.
I have seen many individuals who make a regular habit of severely BMing opponents and trolling lower-div teams/new players, yet they are considered funny and their circles get very loudly pissed off when these individuals catch any consequences at all (whether league bans or social consequences). As harmful as this behavior is, not to mention so much worse and more prolonged than the OP’s outburst, I would certainly not wish for them to be harassed in the same way.
Second.
This is a bit of a message in a bottle, and I’ll bet most folks won’t even read through it, but if it reaches even one person who is slightly willing to listen, then I will try:
It’s really, really difficult to imagine anything other than the way it is, if you’ve spent your whole online life in communities where harassment, casual bigotry, and so on are the total norm. It may not even register as such – “oh, I’ve seen worse”, “oh, it’s not like anybody meant it that way”, etc.
The thing is that just because worse things exist, or just because someone didn’t “mean it”, doesn’t magically erase the negative consequences – the hostile environment that is being maintained by those habits and norms. And it doesn’t actually have to be that way! There are online communities – small, grassroots-style competitive gaming communities, even! – which are not like this, which thrive on making themselves welcoming, encouraging places. It can be so difficult to imagine if this is all you’ve experienced, but I promise you, it’s a thing.
And, just because a community has a history of particular norms doesn’t mean it always has to be that way. Nor does the fact that one individual has a history of participating in, promoting, or turning a blind eye to particular behaviors mean that they always have to do that either. The important thing is what you do, right? Repair the damage that has been done, if you can and if the other person is willing. Learn from the past. Practice and improve for the future. The stakes are bigger than a videogame, but the process and mindset is pretty similar, I reckon.
The world is a complicated and full of ups and downs. But given how bad the downswings can be, isn’t it better to try and make the rest as good as possible? Rather than building one’s identity defensively around Not Caring, isn’t it better to reduce the need for that defense mechanism? Rather than “how dare you impose limits on toxicity” or “life sucks, deal with it”, isn’t it ultimately more meaningful to ask “how can I make life suck less, both for myself and others”?
You (we) (everyone) can do better. You (we) (everyone) always did deserve better.