A rationalization means to come up with reasons to support a belief, idea or action that one knows (or could know) is not actually rational. It is a form of dishonesty mimicking rationality. The issue with smart people is not that they rationalize (i.e. are dishonest) but they are able to come up with sincere reasons, often very convincing reasons, for their beliefs. This makes it very difficult to get them to question their premises.