The biggest advantage of extremism is that it makes you feel good because it provides you with enemies. Let me explain. The great thing about having enemies is that you can pretend that all the badness in the world is in your enemies and all the goodness in the world is in you.
Attractive isn't it? So if you have a lot of anger and resentment in you anyway and you therefore enjoy abusing people, then you can pretend that you're only doing it because your enemies are such very bad persons! And if it wasn't for them, you'd be good natured, and courteous, and rational all the time. So if you want to feel good, become an extremist.
You can strut around, abusing people, and telling them you could eat them for breakfast and still think of yourself as a champion of the truth. And not the rather sad, paranoid schizoid that you really are.
More likely "I'm one of the good ones, and I will use my authority to force you into believing that"
-- John Cleese
https://youtu.be/GeixtYS-P3s&t=13s