They probably don't want to associate with "normal" people because they revel in their "weird" status.
Which, honestly, is kind of understandable and relatable. People are often mocked and reviled for sticking out, for being different. It makes a sad sort of sense that they'd lash out at those that represent that "normalness" that they're told they'll never achieve.
I certainly don't think it's healthy in the long term, but I can at least fathom the logic that got them there.