A study about the ideological beliefs of professors has come to the attention of the blogosphere. and Volokh has some thoughts on why the clear liberal bias in college faculty is bad.
I think a more interesting question than Why is this bad?, is Why does this happen? This is the first step to discovering more about how to rectify the problem.
My initial thought about this study is that they used self report data. Someone who works at a more liberal school may be more likely to identify themselves as liberal regardless of actual political affiliation. (For instance, I would identify myself as fairly liberal, but I don't know if I actually am.) A belief system such as this is very subjective and it is difficult to measure someone's "liberalness" without first looking at their beliefs on individual topics and using that as an index of their beliefs. To just ask means you might not get accurate results.
Interestingly they did break down some issues and found that professors were mostly liberal on these issues (Abortion, homosexuality, the environment etc.). Using an index and found similar results to the self report data. Both models indicated that more conservative professors tended to teach at lower quality schools.
So now that I have looked at this study and found no fault with it (Disclaimer, I only have a BS and I'm lazy, so there still could be problems, but I'll leave that to the academics who get paid to review studies) we can discuss other reasons for why they would get these types of results.
I would like to point out that I am comparing Academics to non Academics and not Liberals to Conservatives. The proportion of liberals in Academia is much higher than that of the whole population, why is this?
Let's start with the conspiracy theory and have it out. Liberal academics hold the conservatives out of the academic world by refusing them tenure, not publishing them etc and so forth discrimination wah. I don't agree with this mostly because it is my experience that the higher up in a liberal university you go the more conservatives you find, the board of directors of most universities is made up of rich guys and I have trouble believing that all of them are liberals too. I could be wrong, but just as I refuse that there is some conspiracy keeping women out of scientific fields I refuse that there is a conspiracy keeping conservatives out of schools. It is just too easy.
My personal reaction is to say that that is because Academics are more likely to evaluate something critically and scientifically than non-academics, and that these evaluations lead more of them to a liberal conclusion. I would like to believe that this is wrong, so I will move on.
Another thought, maybe individuals who are more liberal are more attracted to academia. There is typically a lot of work, and not a lot of pay. There is no Christmas bonus, and on purely economic basis, being a professor sucks unless you get a lot of cushy consulting jobs. Are liberals more attracted to this kind of environment, my magic 8 ball says "Yes, Definitely" but it lies all the time.
This is my third thought, a self fulfilling prophecy. Because there are so many liberals, only other liberals are comfortable in academia. Just like there are few conservatives rushing to move to San Fransisco there are probably few conservatives dying to be on a faculty with gay men and feminazis.
And finally, all academics have been brainwashed by the academics that they learned from. I am a liberal zombie, me eat republican BRAaaaaaaaaaaains. GIVE ME BRAAAAAAAINS!