Since the LARP wasn't credible, I don't think he did anything that was all that big a deal. Probably (1) people were looking for an excuse to get rid of him anyway, and (2) it seemed likely he would continue attempting suicide by admin to try to get himself forced off the forum, so banning him seemed like a way to avoid further disruption.
He's probably a misfit who can't find anywhere else to post where people will engage with him and not ban him. Maybe he should create his own forum, "Fontaine's Hangout," or something, to challenge assumptions and discuss the pressing philosophical issues of the day. I doubt it'll happen, though.
Probably there was simmering resentment against him for a long time, but people gave up talking too much shit about him, because they figured it was hopeless trying to get him kicked off. Then when he
actually did break the rules, they feigned outrage at the LARP to nail the door shut against him coming back.
All this could've been avoided if he'd gotten an anime avatar so that the halo effect could've saved him. It would've triggered that same impulse that makes parents say, "Wow, this kid really misbehaved.. she's so cute though.." It's hard to feel that way about Tom Cruise; even if he is good-looking, he's not kawaii.