Pretending that your political adversary is crazy -- rather than merely misguided, mistaken or misinformed -- is a relatively recent strategy of political partisans. It coincides with the rise of the pseudo-intellectual among the country's cultural elite.
There are lots of ways to identify a pseud, that over- schooled, undereducated poser who places the highest value on appearing sophisticated rather than on sophistication itself.
One mark is his belief that whoever disagrees with him must be intellectually deficient somehow -- the owner of a mind far punier than the finely tuned organ the pseud is fortunate to enjoy.
But assuming the stupidity of other people gets boring, and pseuds have short attention spans. And sometimes one's political opponent seems too crafty to be merely dumb.
That's when the pseud calls in the heavy artillery of bogus psychologizing. The fellow with whom you disagree is not merely a dope, he's a nut. And the surest evidence of his psychopathology is -- that he disagrees with you.
Of course, people who disagree with me are nuts--or stupid.
Via John Podhoretz.