Imagine you have a prvocative member. S/he provokes everyone. S/he goads people, criticizes every idea and is universally hated by the community.
Should s/he be removed? Sometimes, sure. However...
Provocative members perform an interesting role within a community. They unite the community against them. They establish traditions within the community. They create common goals and a stronger sense of community amongst members.
The provocative member may be good for the community. This is true for many things the community dislikes. The unity in disliking may be a great solidifier for the community. You remove remove the provocative member and find that activity and the sense of community amongst members drops.
This isn't to say that you should or shouldn't ban provocative members. It's to say that it's more complicated than it appears. You don't remove members you (or the community) dislike, you remove members that aren't good for the community. They're not the same.