I know from personal experience at NYU over the years that it's NOT because graduate students who are entering the professoriat are more liberal. It's because hiring committees are more liberal.
Conservative hiring committees usually hire the best candidates, regardless of politics. Liberal hiring committees always hire clones of themselves, and wouldn't touch the best candidate with a ten foot pole if he was a conservative.
The result is that almost all the chairmen and hiring committees are now liberal, and their departments keep moving further and further to the left. Not only that, but many departments have been wrecked because no one is interested in doing anything but politics or gender studies.
... proving once again, that diversity for liberals is purely racial. Idological diversity is not desired or embraced.
I was truly shocked when I found out that something called "Queer Theory" is taught with a straight face at some schools.
Well said. The power is in the hiring committees and the leftists have determined to stack them.