Fundamentalism is normally used in a religious context, but I submit that there are "fundamentalist" liberals, conservatives, etc. Just about any belief can be taken to an extreme, which everyone here likely considers a bit dangerous.

An example would be Constitutionalist Fundamentalism, the idea that the nation should adhere to the Constitiution, to the exclusion (or invalidation) of any subsequent law or regulation.

Or Environmentalist Fundamentalism, where the environmental concerns are championed over any and all others, like economics or human development.

Fundamentalism is basically extremism. A narrow minded focus on perhaps one interpretation, and steadfast adherence despite outside information that may cause "cognitive dissonance".

__________________
The poor object to being governed badly, while the rich object to being governed at all. -- G. K. Chesterton