Yep, fundamentalism is a cognitive predisposition rather than a rationally adopted view. I've seen that, inter alia, among Polish immingrants in this country - the most ardent anticommunists used to be party apparatchiks in their previous lives. The fundamentalist mindset is like a low resolution camera - it is unable to process complex multidimensional information, and reduces every image to crude white and black blocks. The colors of these crude blocks are easily interchangeable, which explains why fundamentalists switch ideologies so easily, but their cognitive style remians essentially the same.
IMHO, fundamentalism is a mental disorder that, like schizophrenia, have a not yet understood neurological basis. Hopefully, with the progress of neuroscience we will be able to diagnose and remedy this condition. Unfortunately, as Stanford psychologist Philip Zimbardo once said, if one man's delusions are shared by others, they become a political point of view, protected by constitutional rights. That may pose some obstacles to treating that mental disorder.
Wojtek