I consider this a medical/psychological issue. Thinking in a rational way can co-exist with fully biased lunatic and insane beliefs plus insane behaviour that contradicts their own mind. In humans can exist conditions that fully overwhelm any reasonabel way of thinking. Usually it is the Cerebellum. This is that part of our brain that we share with animals and our old ancestors that harbours automatic reactions on fear, panic, love, excitement and such. When under an impression of existential fear this can totally kick out sense. And fear must not take the form of shivering in a corner, it can take the form of aggression of most brutal ways. When zeal takes over it blinds the mind in many ways.