Winston Churchill reputedly quipped that fanatics are people who cannot change their minds and will not change the subject. He got their epistemology just right in his first point. But perhaps he got them wrong in his second point. It is not so much that they will not change the subject. Rather, they cannot change it, because they have no other subject. That is the nature of their crippled epistemology, without which they would not be fanatics.
Russell Hardin, in Political Extremism and Rationality.