There's a fascinating discussion thread at Quora on this question--check it out. First of all, I am not disputing the premise: This Pew survey, for instance, found that
More than half of the scientists surveyed (55%) say they are Democrats, compared with 35% of the public. Fully 52% of the scientists call themselves liberals; among the public, just 20% describe themselves as liberal.
So, scientists are, in aggregate, more liberal than the rest of America...but why? I am not going to be satisfied with a "really smart people are liberals" kind of answer. I know too many smart conservatives. Other arguments that I've seen in the thread that sound more plausible:
1. Republicans have taken a lot of anti-science positions lately (climate, evolution, etc) and scientists are just responding to that. 2. Academia is a very liberal environment, and that's where scientists cut their teeth. 3. Smart and talented conservatives don't hang around for a Ph.D., they want to get out of the ivory tower (which they perceive hostile anyway) and into the business world.
What do others think?