It may simply be because they start out holding one nonsense notion, which is sufficiently divorced from reality to impair their ability to evaluate the merits of claims in general. If such an individual meets with an organisation that - ah - does not stress critical thinking skills, shall we say, it's entirely possible that this person will adopt its dogma more or less wholesale. Certainly, crank magnetism appears even in more loosely associated groups (see, e.g. the cross-pollination between YEC'ers and germ theory "skeptics"), so there's no reason it shouldn't happen in a structured environment in which adoption of the entire dogma is actively encouraged.

And weird ideas don't come and go - they accumulate: Having no basis for sifting the nonsense from the sense, dismissing any part of the dogma will run the risk of alienating part of the group. And since consistency isn't terribly important to this kind of mindset, it's easier to simply insist on all the dogma that the group has happened to pick up along the decades.

That's my amateur psychology anyway...

- Jake

Friends come and go. Enemies accumulate.