Skepticism, Science & Pseudoscience

There is lots of evidence that education is correlated strongly, whether as cause or effect or probably both, with IQ. There is also evidence that education is inversely correlated with prejudices. So the association between low IQ and prejudice is to be expected.

More cynically, it may also be that more intelligent people realize that the socially acceptable way to answer these questionnaires is to deny prejudice; and that people with low IQs are less alert to this.

As regards conservativism: some of the right-wing messages explicitly pander to prejudice, which is not to say that ALL right-wingers are susceptible to these prejudices.

I think what is most likely is the following:

People of any IQ level may be Conservatives, but often for different reasons. For many reasons, that operate in both directions, IQ is correlated with occupational success, which is in turn correlated with earnings. Those people with high IQs, who are Conservatives, are therefore most likely to be so due to economic self-interest: they are often fairly high earners, and may be reluctant to pay taxes to help poorer people. People with lower IQs tend to be less occupationally successful, and, unless they come from well-off families, are therefore on average poorer. Therefore, if they are Conservatives, it is less likely to be due to economic self-interest, and more likely to be due to prejudices, to which they are extra-susceptible due to their lower education, and to which the Right tend to pander in order to get their vote.