I agree that in a vacuum people are equally likely to believe bullshit regardless of their ideology. I think in practice however due to the impact of the media that conservatives tend to consume, the bias of media towards an imagined balance, and the lack of almost any concrete policy objectives on the right that they are more likely to believe nonsense because they are exposed to more of it. Whether or not that is the result of some underlying difference or just a coincidence in how media networks developed, who knows, but liberals simply lack the same sort of media vehicles such as Fox News or right wing talk radio. Not only is it not there, when it's been tried it has failed due to lack of interest.
I personally think our divide is primarily the result of the fact that our brains are wired to interact with people in a fairly close group of people we know pretty well and mass media has made that no longer the case. It's easy to think that other people are dumb and bad if you've never had them over to dinner. (okay, it's often easy to think so after dinner too, but still)