Lots of LWers are libertarians, far more than in the general population. Also a significant subset of Libertarians like to think of themselves as being driven by reason (which I think is a situation somewhat similar to the one with polyamory btw).

Obviously this dosen't imply that Libertarians will on average be significantly or even measurably more rational or less blatantly stupid, but hey our brains are wired to be stupid in that way! :)