I wanted to get that out of the way in part because I'm writing a book that covers much of this territory, but also because I have a low tolerance for anyone, let alone scientists, lumping American conservatives with socialist German mass-murderers. Call me thin-skinned, if you must.
Anyway, Jack Glaser, one of the lead authors of the Berkeley study, acknowledged in a media release that a study focused solely on why right wingers aren't right in the head might seem "partisan." But, he explained, there is a "host" of information available about conservatism and comparatively little about liberalism.
But why, exactly, haven't they studied why people are liberal? Perhaps it's because the profession thinks it's "abnormal" to be a conservative in the first place.
After all, psychiatrists study why people murder or why some people believe they're Napoleon or why they think Carrot Top is funny. But they don't study people who take showers. Why? Because taking a shower is normal, and therefore uninteresting. Perhaps it says something interesting about a profession that sees conservatism as so abnormal so as to be worth studying.
If you go back and look at the list of characteristics that define conservatism, you'll discover that it applies to liberals, too. Fear of ambiguity, a desire of cognitive closure, etc: These are human traits, not conservative ones.
Plenty of liberals refuse to accept that a factory closing can be a good thing or that something other than racism is to blame for the problems blacks face. There are liberals who will tear your eyes out if you say that the 1964 Voting Rights Act had problems or that it's not clear Head Start is worth the money.
These scientists went off to find negative traits, and when they found what they were looking for they stuck in a pin and said, "Here's a conservative." This is the equivalent of only looking for your car keys where the light is good. In short, they started from a position of cognitive closure. So I guess they were conservatives after all.