What a valuable post! Allow me to make three points. First, I think the plasticity of our views might have been slightly overstated. You knew someone who became a fundamentalist for six weeks and then rejected it. Most people do not change world views twice in two months. I suggest that people who change world views may have triggering events which commence the process of change, but, normally, change takes time. The second point is that, while you are correct that, while a person should identify and reject maladaptive beliefs and behaviors, a person might also benefit from trying to understand what produced them and also whether they might have to change their social situation to be free of them, e.g., their community, their marriage, etc. Third, ones worldview must be coherent with the world as you observe it. It might not be healthy to see yourself as surrounded only by enemies. You can make yourself be aware that there is much good in the world. But you cannot blind yourself to evil.