This posting from senate Underground hass an awesome explanation of the differences between fundamentalism and religion :

It seems to me like the thing that really *is* in opposition to the senate/liberal/progressive philosophy is not religion, but fundamentalism. Fundamentalism is what happens when you pick one particular set of beliefs and decide that a) they are the ultimate answer to life, the universe, and everything and b) anyone who doesn’t share buy into this belief system is the adversary and must be either converted or destroyed. Fundamentalism is a problem in a heterogeneous community because it’s intolerant of difference, and it’s a problem in general because it discourages independent thought, enforces ideological rigidity, and leaves its adherents not only unwilling to compromise in the face of necessity but unable to learn and adapt to new information if it contradicts part of their world view.

OK, nothing earthshattering there. Now. Here is the thing.

*Fundamentalism does not necessarily have anything to do with religion.*

You can be a fundamentalist about anything. My brother is a capitalist fundamentalist. He’s got no use whatsoever for God, but imply that the ideal of free market competition is a myth that is never realized because capitalists always try to rig the game to their own advantage, and watch the missionary zeal emerge. White supremacists are fundamentalist when it comes to their theories about racial superiority. Not only will they refuse to be swayed by anything other people would consider evidence or logic, but–and this is true for other fundamentalists too–they use their pet theory to explain EVERYTHING. Global warming, Celine Dion, doesn’t matter, it’s all somehow the fault of people who don’t recognize the natural superiority of the white man. Same thing with people who are America supremacists. America is always better than everyone else. No, I don’t care how many poor people we have or how bad our economy sucks or how corrupt our political system is or that we’re torturing people and everyone’s OK with that. America is supreme, it deserves to be supreme, and if you try to tell me otherwise, you must be a traitor, which means that all that shit you were talking about is your fault anyway.

And, and this is my main point, there are fundamentalists on the left too. And folks, you don’t want to become fundamentalists, because it will make it impossible for you to know when you’re wrong about something or to figure out new strategies for new problems. It’s one thing to stick by your principles, and it’s another thing to refuse to admit the legitimacy of any other point of view.

One of the big problems with the way things are right now is that because the right wing has been taken over by fundamentalists of all kinds, their extremism is pushing us into a kind of mirror fundamentalism, where we feel we have to be extra-rigid about our own beliefs because they’re constantly under attack. While I absolutely believe that it is crucial to present a united front in public, and I also believe that our party leadership has screwed itself and us by NOT being willing to stand up when attacked, I also think it’s a mistake to refuse to change just because you don’t want to look weak. Cause we know where “stay the course” ends up, don’t we. A giant fucking quagmire that’s on fire, that’s where.

We’ve got plenty of fundamentalists on our side as well who have their own pet “single-cause theory” about why things are so screwed up. Every time somebody tries to tie everything back to corporations or “the media” I get bored. Not that those aren’t big areas for concern or anything, it’s just that we’d all be better off if we stopped pretending that we’re a single battle away from fixing the messes we’ve foudn ourselves in.