Seems to me like only the tiniest minority of threads get shut down judging from the locks that are visible. And they're only shut down when they seem to be potentially generating hate or racism or name-calling or something really rank that's liable to cause more problems by continuing than by being shut.

My forum where I can just "bitch and argue and stuff" is my house, but I find it has the same effect there that chronic bitching and arguing do here. Makes folks less likely to want to talk to me nicely in return. So I generally exercise when I feel like bitching.