My respect for Amazon's founder Jeff Bezos (new interview) just increased tenfold. Apart from some spiritual teachers, I've don't recall hearing anybody say that one should not only be able to change one's mind frequently, but also even occasionally re-evaluate one's basic convictions. So beautiful. It has been perhaps the one most important thing I have learned in my life, and I came late to it. I think it's one of the hardest lessons to learn and apply, it is an ongoing process, for the mind is heavily geared to protect beliefs with our deep-seated human fears.
How deeply it is ingrained is evident (as Bezos also points out) from the fact that in politics it is suicide to change your beliefs. The broad public will instantly perceive you as weak and wishy-washy, and people want strong leaders, I guess because they want them to suppress their enemies for them.