[ACPlayer]

By the way, it's also true that by far most college professors are liberal or left-leaning, Democrat rather than Republican

I would tend to agree that most professors are liberal, if you limit the topic to social liberalism. That is they are more likely to be pro-choice, anti-guns, for human rights, prefer peace to war, against the death penalty etc.

I also suspect that this has to do with the fact that they are generally better educated than the general population. Good education generally makes people more willing to challenge the status quo (and social conservatives are more likely to want to keep the status quo) and believe that there may be better ways to do things than what has been previously been done.

I dont know if college professors are economically more or less liberal than the populace.