If you think in terms of empiricists vs. non-empiricists there is nothing rational about either of those positions. If you think in terms of "dumbest republicans and dumbest democrats" I still don't think there is anything rational about those positions, although I suppose it might be explained by the laziness of party affiliation. [Democrat should probably be replaced with "spiritualist" or something like that, since the democratic party does not contend that vaccines are dangerous in the way that the republican party contends that climate change is a conspiracy, but you get the idea.]

I don't think the large number of independents that believe truly absurd things can be explained without irrationality, in any case. Also, the policy positions held by prominent political figures on the right is not an analog to beliefs held by a small number of fringe elements in hippie communes on the left. This seems to be trying very hard to say, "eh, we're all crazy!" when the crazy is primarily on one side of the coin.