One reason why "deranged" rhetorical excesses proliferate in our political discourse is that most partisans are far less willing to condemn their own side's excesses than those of the opposition. Some of this is caused by simple bias and ignorance.

But some of it is also partly caused by a belief that your own side's rhetorical excesses are merely exaggerations of an underlying truth rather than completely wrong. Consider for example conservative charges that Barack Obama is a "socialist." I think that such claims are absurd. At the same time, I do fear that Obama is likely to vastly expand the scope of government and that some of the policies advocated by him and other liberals have flaws that are similar to those of full-blown socialism. From my perspective, there is a very important difference of degree between the two. But there isn't always a difference in kind. I think that "Obama is a socialist" accusations are seriously misguided and would never say such a thing myself. At the same time, it's hard for me to be as tough on those who make them as I would be on people whose rhetoric is in my view completely divorced from reality.

Consider, on the other hand, liberal charges that McCain and Palin are engaging in "racist" campaign tactics. Thoughtful liberals probably reject claims that McCain is a racist or even deliberately pandering to the racism of others. But many of them also believe that such charges are merely an exaggeration of the underlying reality that the Republicans have long sought to exploit racism for political advantage with their attacks on affirmative action, welfare, and so on. I actually think there is a measure of truth to this broader charge against the GOP, though not as much as many liberals believe there to be. Part of the reason why many liberals are reluctant to denounce the "McCain-Palin are racist" meme is that they think it reflects a deeper truth to a much greater extent than I do.

In sum, it is extremely difficult for people with strong political commitments to be as hard on their own side's "deranged" rhetoric as they are on the opposition's. Some of this is simple bias and hypocrisy that they have little incentive to correct because of rational political ignorance. Some stems from a genuine belief (albeit also influenced by bias) that their side's excesses are less blameworthy than the opposition's because they are merely exaggerations of an underlying truth, whereas the other side's are flat out wrong.

I don't have a good solution for this problem. But the beginning of wisdom is to at least be aware of it, and to try to remember that it applies to you as well as your opponents.