There are many smart left-liberals, conservatives, and libertarians who will probably never agree about politics no matter how long they consider the same evidence, and argue. They just have different conceptions of right and wrong, and human nature, what people should be forced to do and what they should be free to choose.
Randy Barnett wrote a post at the Volokh Conspiracy blog yesterday discussing this article from Liberty magazine, and opened up comments for libertarians to try to explain their own psychology. If you’re curious about the psychology of political ideology (as I am), I encourage you to read the article, the post, and the comments.
I don’t know what the answers are. I don’t think many of us are very good at introspection about why we have formed our deep assumptions, and we’re even worse at figuring out what makes others tick. But, I think there’s an element of the truth in much of what is suggested by these thoughtful people speculating about it.