All authority has the same agenda, doesn’t matter which religion, political party, or country, extreme or not, it’s simply there to give people a quick answer based on their belief systems, to find things out for yourself is very difficult, so most people opt to be slaves of their own minds by following a perceived authority. 

 Extremists all share one thing in common, the inability to perceive shades of grey. Everything is either black or white. I suspect IQ plays a role in this.