Discriminations points to a symposium held at Duke on the lack of intellectual diversity there, which we've heard much about. While much of it is the usual back-and-fill defense, poli sci chair Michael Munger is really, really good. Even if you assume 90% of historians are Democrats, there's only a 2.5% chance of finding no Republicans in a history department of 35 faculty members chosen at random. Here are some other quotes:

Here's a true statement: ... every conservative faculty member recommended for by the literature department has been tenured. That's also true of every unicorn and every talking dog, so it's a vacuously true statement. ...

Being conservative is by definition not intellectually respectable. Conservatives are simply not qualified. That was not an administrator, that was no person in a position to put that into effect, but I think it's a widely shared view. So the claim that most of the qualified applicants are Democrats or even more liberal than Democrats is probably true. It would explain why most faculty in the social sciences and humanities departments are not conservative. But it would not in itself explain why there are no Republicans. The problem is not too many Democrats, the problems is too few Republicans to be able to say it is an ideology-blind process. There is no other explanation for the overwhelming disparity.

Q.E.D.