But there is better reason why university faculty tend to be liberal. It is that the university is inherently a liberal institution. To keep a democratic republic going, you're always going to have to move against the current. The university is the place you learn to swim, not so much in what you learn, but how you learn. Personal freedom, skepticism, erudition, rules of evidence, equality, secularism--you might as well be describing the very foundations of the classroom experience. It is meant to incubate doubt and mentoring and the equality of merit.
For these conservatives, the university is just the kindergarten's finishing school. It is the place where received wisdoms are received most perfectly. They talk about freedom, but think of this (also like Hegel, alas) as the recognition of necessity. They think of education as the way the nation indoctrinates new generations to the values (also above averageness) of the nation. Teachers who, rather, emphasize liberal ideas are a danger to their mobilization and solidarity. They will rail against the danger of professors' biases when professors are really biased against holding biases--which is exactly what these conservatives resist. As Didi says, follow the money back to the Hudson Institute.