>appears to actually make people more susceptible to nonsense

I think it is more that teenagers and very young adults and people high in the trait of "openness to new experiences" are more susceptible to nonsense and more attracted to new intellectual movements, of which the rationalist community is one.

Also, I expect a rationalist to be lower in conscientiousness than average (because the conscientious people are too busy to devote a lot of time to reading long intellectual texts) and low conscientiousness makes violence and other transgressive behavior more likely.