but their very extremism tends to alienate others, ultimately undermining their effectiveness to get anything done.

Long before I heard the term "PC", I saw it in action from the most radical feminists. This was during the campaign to ratify the Equal Rights Amendment (ERA). All in all, the ERA appeared pretty straightforward and many states approved it. However, rather than sitting back, the extremists were busy behind the scenes being language cops. Some of their pronouncements were just silly, such as "womyn" (they were against the word "men" just about everywhere it was used). Ultimately, they became a laughingstock. It'd be hard to quantify it, but their absurdity was so blatant that it became easy to oppose them and that might've been a factor in the ERA's failure.

Of course, the extremists from the other side like Phyllis Schlafley (sp) were just about as silly with their insistance that the ERA would result in things like "unisex bathrooms in schools" (Horror - that'd be just like the ones they have at home!).

By and large, the majority of the American electorate tends to reject extremism from either side, be it Goldwater's "Extremism in the defense of liberty is no vice" speech to McGovern's and Mondale's campaigns. Without a majority, you can't win enough elections to have any power.

I think this is why so many Democrats are trying to paint the Bush administration as a bunch of extremists for just about every issue. Unfortunately for them, they're so extremist themselves that I think a lot of people are tuning them out. That's good for my side, though, and I'm enjoying watching them self destruct.