Noah Millman wrote an excellent essay which asks "Who closed the conservative mind"
However, he doesn't even consider the obvious candidate.
Ronald Reagan was very ignorant and confidently made claims (say about where we were on the Laffer curve) which have since been decisively refuted by the evidence (and in fact were inconsistent with evidence available when he first made them). However, one can not be considered a conservative if one criticizes Ronald Reagan. I think this means that all open minded people are excluded from the conservative movement.
In particular, the celebration of ignorance and the contempt for reality ,which are clearly common in the conservative movement, are directly and very very explicitly justified by references to Reagan. Consider Norman Podhoretz. He says he likes to torment conservative critics of Palin by noting that their criticisms of Palin sould just like their criticisms of Reagan in 1980. This is held to be proof that the criticisms are invalid.
No movement which places someone above criticism can be open minded. Nothing could be less plausibile than the idea that open mindedness might survive in a movement which places someone who was completely fact resistent above criticism.