There are "fundamentalists" in every faith, including the faith of people who would deny they have any faith.

As he often managed to do, Bob Dylan has a tag that fits:

In a soldier's stance I aimed my hand
Ay the mongrel dogs who teach
Fearing not thta I'd bevome my enemy
In the instant that I preached.

I agree with John H that it is unfortunate that the term "fundamentalist" gets adopted by, and used as a label for, people who are, through their intolerance and openness to hate and violence, opposed to the fundamental principles of the religion they claim to represent. And I don't just mean Christian fundamentalists here either.