I think I would mostly agree with your definition of fundamentalism - I just would be careful with that "binary views" thing, as that indeed often is a characteristic of fundamentalists, but it's not a defining characteristic. I also have very binary views about slavery - but I think I could give you well-founded rational arguments for my position. This is often not appreciated, but there are plenty of questions where there is no gray area whatsoever, so a view that does not allow for any compromise whatsoever can actually be perfectly rational (the only "gray area" of sorts is that any rational argument can be attacked at its premises, but there just are some premises that are sufficiently well-founded empirically that noone really expects them to ever be invalidated). Also, not everyone who thinks that we would live in a utopia of sorts if we followed their lead is necessarily wrong, as you also can see from history: A world (kinda) without slavery really seems to be a far better world, even if it might have seemed totally utopic back when slavery was normal and people who advocated for abolishing slavery might not have been particularly popular.

Now, I never said fundamentalism (by that definition) was good. I only applied exactly what you are saying to what you were saying: People who fight against fundamentalism for the wrong reason are doing the wrong thing. There are good reasons for fighting against fundamentalism, "fundamentalism is bad because it's bad" is not one of them, as that is just dogma, aka blind faith, aka fundamentalism. But I guess you did already understand that - though it's not at all similar to the case of "intolerance of intolerance", except at a very superficial level. There is a contradiction between "advocating for a world without intolerance" and "defending the intolerance of people", which is why that conflict has to be resolved somehow, and it's easy to resolve it in such a way that "intolerance of intolerance" really is a perfectly self-consistent concept that provides real value to humanity (when your goal is to improve people's well-being, there is no contradiction in allowing gay people to be openly gay (tolerance) and also putting people who try to kill gay people in prison ("intolerance")), which is why that "criticism" really doesn't make any sense - it's essentially just being obsessed with a word which has a somewhat ambiguous meaning. It is perfectly possible, though, to provide rational arguments for why fundamentalism is bad, ultimately grounding it in almost universal preferences like avoidance of pain, suffering, sickness, ... - I did provide one rough version of such an argument in my last post. That's why "fundamentalism is bad because it's bad" is bad.

Now, it's obvious that those same rules do apply to the FSF and RMS, but I doubt there are many devout RMS worshippers. And if you were trying to imply that RMS was a fundamentalist - well, I guess I would suggest that you try to understand his position and his arguments, because, you know, he does actually have arguments, and those are not quotes from a holy book, but actually rational statements based on explicitly stated premises. When doing that, you might even see that he understands the gray areas around his position very well, it's just not his primary job to promote the gray areas - but if you don't call Bill Gates a fundamentalist because he doesn't promote Debian, possibly calling RMS a fundamentalist because he doesn't promote proprietary software isn't quite appropriate either? One certainly can disagree with him on things, but claiming that his world view was purely based on dogma says more about you than about him. Now, maybe I am putting in your mouth what stephenr said, in that case take it less personally ;-)