Reacting to a new study on academia’s left-leanings, Megan McArdle explains how bias could result: 

Unless they are really, really brilliant, academics, like everyone else, need personal connections to help them up the academic ladder, from recommendations to mentors to advisors. Those personal connections are always much easier to make with people you agree with. Nor would I discount the possibility that, just as women’s work can be subtly dismissed because we know women aren’t as bright as men, academics who think that conservatives are stupid would factor that into their assessment of someone’s intelligence–and then factor that assessment into their assessment of someone’s work. And of course, one’s ideas are to some extent socially constructed; simply by virtue of the arguments and information we hear, even if there is no social pressure to conform, being surrounded by a political culture will tend to drag our ideas in their direction.

And the idea that academia exerts no pressures to conform is spectacularly hilarious to anyone who’s ever spent any time at all around academics. Perhaps the funniest sight I have ever witnessed is the spectacle of a sociologist cruising straight past the analyses of power relationships and group norms that they apply to every single other facet of human existence, and insisting that the underrepresentation of conservatives in academic could only be explained by the fact that conservatives are a bunch of money-grubbing intellectual lightweights who can’t stand rigorous examinations of their ideas, and moreover are too intolerant to fit into the academic community.

The sociologist, you see, is inside academia, and so able to analyze it better than outsiders. Also, the sociologist knows that neither they, nor any of their friends, is biased, so the answer must be that there’s something wrong with conservatives.

It’s odd, given this lack of bias, that one repeatedly hears from untenured academics who are in the closet. "Passing" is not usually a behavior one finds in a community where there is no prejudice.

Ironically, itself illustrates this point nicely.  It starts with a long rant complaining that this subject has had too many sloppy studies by ideologically motivated conservatives, such as my colleague Dan Klein, so thank God they can finally offer us an objective analysis.  And then they completely confirm Klein’s results.  Noteworthy details from the study include that support is nearly equal for Israel and Palestine, and that only one quarter think discrimination is the reason for fewer women scientists.