Memetic Immune System
Intelligent people sometimes do things more stupid than stupid people are capable of. There are a variety of reasons for this; but one has to do with the fact that all cultures have dangerous memes circulating in them, and cultural antibodies to those memes. The trouble is that these antibodies are not logical. On the contrary; these antibodies are often highly illogical. They are the blind spots that let us live with a dangerous meme without being impelled to action by it.
-Phil Goetz, Reason as memetic immune disorder