I guess it depends on how you're defining the term "fundamentalist". I'm from the US, and generally when people use that word here, they are either talking about religious fundamentalists, or they are making an unflattering comparison between religious fundamentalism and a person's beliefs about something else which isn't religion.
I associate that term with people who adopt a specific point of view on faith, rather than from a long process of observation and reasoning. They don't change that point of view, and at no point engage in any ongoing observation and reasoning to revise their view, once it's been adopted. They also tend to have very simplistic, binary views on the subject matter ("x is evil, y is good, and there are no gray areas between them"), and their views are as much or more about making people feel good about themselves than anything else (they get a rush out of feeling like they know the truth, and we could all be living in a utopia if only everyone would listen to them).
So, based on that definition, yeah, fundamentalists are bad, even when they happen to be fighting for something you might agree with. It's like a broken clock being right twice a day- just because they're right about something at this moment doesn't mean people should emulate them or buy into all of their other beliefs. In fact, doing so would make the world a worse place, not a better one. By all means, fight alongside them if they happen to be doing the right thing, but be wary of them in all other respects, and don't take anything they say at face value. Don't dismiss it out of hand either, just maintain a reasonable amount of skepticism about such people. I include RMS and the FSF in that group.
Now, I can totally see how someone might say that what I wrote above is a fundamentalist criticism of fundamentalism. I get it. It's sort of like people who complain about other people being intolerant of intolerance. It's kind of a tautology, but that's how I feel (for the record, I am also intolerant of intolerance, so guilty as charged).
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 ;-)
I associate that term with people who adopt a specific point of view on faith, rather than from a long process of observation and reasoning. They don't change that point of view, and at no point engage in any ongoing observation and reasoning to revise their view, once it's been adopted. They also tend to have very simplistic, binary views on the subject matter ("x is evil, y is good, and there are no gray areas between them"), and their views are as much or more about making people feel good about themselves than anything else (they get a rush out of feeling like they know the truth, and we could all be living in a utopia if only everyone would listen to them).
So, based on that definition, yeah, fundamentalists are bad, even when they happen to be fighting for something you might agree with. It's like a broken clock being right twice a day- just because they're right about something at this moment doesn't mean people should emulate them or buy into all of their other beliefs. In fact, doing so would make the world a worse place, not a better one. By all means, fight alongside them if they happen to be doing the right thing, but be wary of them in all other respects, and don't take anything they say at face value. Don't dismiss it out of hand either, just maintain a reasonable amount of skepticism about such people. I include RMS and the FSF in that group.
Now, I can totally see how someone might say that what I wrote above is a fundamentalist criticism of fundamentalism. I get it. It's sort of like people who complain about other people being intolerant of intolerance. It's kind of a tautology, but that's how I feel (for the record, I am also intolerant of intolerance, so guilty as charged).