Just a note, although I know the colloquial expression is "sick and need help", I consider posting things like that an ethical problem, not a medical one. And, yes, absolutely disgusting.
It's too bad you think you need to leave a forum because of it though. People can do that on any forum where they can register easily (including some that require you to fill out a little form before you get approved, it's not like they usually check you out that well). It doesn't say a thing about anybody else here, unless that was a sockpuppet account.
Basically, it's not accurate to claim that because a website has been targeted by a troll, then this says anything about the character of the rest of the people who go there.
Think of it like people who draw hate propaganda on the walls of synagogues. The character of white supremacists defacing the building is in no way reflective of the character of the Jews who go there to worship. And while there are ways to discourage this sort of thing, there is no way humanly possible to fully protect a synagogue against being defaced in this manner.
Same with the people who vandalized a gay community center around here. It had been a safe place for gay people to go without being threatened with violence. Then someone broke some windows and did other stuff to it. The people who went there to get away from hate, are not the same as the people who brought their hate with them when they vandalized the building.
If the moderators saw all this and said it was okay and sanctioned it, that would reflect on the character of the site. But this person has already been banned. What more can moderators do, even if they want to keep a place absolutely child-friendly?
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"In my world it's a place of patterns and feel. In my world it's a haven for what is real. It's my world, nobody can steal it, but people like me, we live in the shadows." -Donna Williams