I've been reading conspiracy websites lately. I find them pretty frightening. Not because I believe what they say, but that these people are absolutely serious. What does that to a person's mind? What makes someone so fucked in the head that they honestly think the world is controlled by alien reptiles(Google David Icke) or that the U.N. is planning to turn the US into a Communist world state? (Google Alex Jones)

What psychological defect would lead someone fabricate these grand and terrifying delusions and defend them to the death?