If they are, then why do they persist as sources of harm?
People's attitudes can be changed by changing their behavior. Get someone to do something, and they'll rationalize why they did so if they can't think of a good reason. Get someone to do something that distresses them, and they'll rationalize very strongly, especially if their self-image isn't compatible with a negative assessment of the action.
Think of really harmful hazing. If no such tradition existed, people wouldn't react well to someone trying to start it. Once people go along with minor hazing, there's less of a psychological barrier against it ...
What do you believe that most people on this site don't?
I'm especially looking for things that you wouldn't even mention if someone wasn't explicitly asking for them. Stuff you're not even comfortable writing under your own name. Making a one-shot account here is very easy, go ahead and do that if you don't want to tarnish your image.
I think a big problem with a "community" dedicated to being less wrong is that it will make people more concerned about APPEARING less wrong. The biggest part of my intellectual journey so far has been the acquisition of new and startling knowledge, and that knowledge doesn't seem likely to turn up here in the conditions that currently exist.
So please, tell me the crazy things you're otherwise afraid to say. I want to know them, because they might be true.