Hmmm...so one common theme that I'm getting as I read the different stories of some (select) fundamentalist movements in history is that they all are reactions to large changes in society.
People who are uncomfortable with changes to the status quo react by reverting back - they look back to a 'perfect' past time that never existed. Religiously minded individuals tend to take the track that if we were truly following the original form of whatever faith they are then this upheaval, this (to them) disastrous change in society won't destroy us. Or won't happen.
And one of the first things they do is start to tell people that all theological or philosophical thought since this 'ideal' time is a part of the problem. That it has removed us from the core, the fundamental of the faith. And they begin teaching people not to think. That they can't think about their own faiths because they don't understand it properly - they have to rely on that particular leader and the interpretation that he has. They close the ability of the people to embrace new thought.
But new thought is important to the survival of any religion. If a religion cannot adapt while still keeping true to the core principles of the faith then it runs a strong chance of dying out or becoming effectively obsolete.