Before I make much more of this, let me say I agree with the conclusion of the article. I think that basic economics training does tend to make people more conservative. Learning basic concepts like cost-benefit analysis, unintended consequences, and comparative advantage is going to take an idealistic college student and teach her that there's no such thing as a free lunch. And to college students who think they can have anything they want and solve all the world's problems with a liberal arts degree, this can be sobering, conserv-atizing knowledge. Additionally, people who naturally think about such things are going to be more conservative for the same reason.
However, I don't quite buy the methodology of the study as conclusive. The questions used seem to be only those types slanted toward a conservative conclusion. I'm sure there are many basic economic concepts that conservatives are knee-jerk against (like "does government spending factor into GDP?" or "do tax cuts always result in increased revenues?") of which one could design a 'test' to show that it is liberals, not conservatives, who are more economically knowledgable.
Lefty blogger Nate Silver explains the vagaries of the questions here.
To reiterate, in anticipation of heat taken: I think that economics training will turn people conservative just as I think that a faithful education and appropriate application of economics will lead to conservative policy prescriptions. I just don't think that this one study 'proves' it. I do think that it can be proven, and that's something that should be undertaken in the future.