To add something useful, I have been in mental asylums. There are physically dangerous people who aren't full of negative emotions. Most psychiatric patients don't have ill feelings towards others in general, only toward themselves.

I have no idea why many hateful minds meet in places like that you mention; maybe it is some specific interactions that spark the noxious emotions, but I am no expert. It is similar to highschool extremely cool kid circles and fraternities, only for reverse reasons (alone together vs in a group)