I tend to be more forgiving of newer MUshers, and generally only shitlist folks who keep doing the same toxic stuff over years.
I don't really accept the 'socially majadjusted' explanation for these behaviors, though. Most MUers are grown-ups, we know how to put ourselves in other people's shoes, and we can empathise. Once again, I give newer, younger MUers more leeway, because they're learning the right netiquette; but at the same time, as human beings who have grown up amidst civilisation, I expect some basic courtesy, manners, and awareness. You don't need to tell people not to sexually harass people, or stop manipulating people to cause drama, etc; they already know this is wrong. (And they hate it when it happens to them, so they ARE aware of boundaries.)
I have NO patience or forgiveness for long-term players who are actively malicious OR extremely 'clueless', because the vast majority of them do know better and just do toxic shit anyway. IMO, they just need to leave. They had every opportunity to be better than they were and they chose the shitty option anyway. This is specifically repeat offenders, as has been previously said, everyone has a bad day and a couple arguments here and there does not constitute a pattern.
I've been in the hobby since 93? Ish. And so in my case, it's resulted in letting a lot of things roll off instead of getting angrier about it: there's a lot of minor-level stuff that people do that is just what people do, especially new people. But I am, as people know, pretty hard-ass and confrontational about a very few things: stalking, creeping, harassment, harem wars, crap like that. All of these things, people know better. It isn't necessary. It isn't beneficial in any way. It just creates more unnecessary toxicity. People who thrive on that just suck and I believe they are too often enabled. They are categorically not welcome in my little corner of the internet (and the feeling is mutual, I know).