The curious thing to me is, the same person can be both rational and irrational. I mean, in the sense of "usually rational" or "usually irrational".
Growing up, there was George. George was a master mechanic who owned a gas station. He was also the chief of the volunteer fire fighters. Close to a hard nose realist.
But George in addition to his other roles, was an elder in his fundamentalist church. If you got into a conversation with him about religion, you'd forget all about his ability to logically, systematically identify and fix nearly any problem a motor vehicle could possibly have, for on religious topics he came across as scatter-brained.
About mechanical things, etc he was able to admit when he was wrong -- often with a sense of humor. On religious matters, he was never wrong.