To participate in democracy as I should I must do much more than say which policies I like. I must offer reasons in support of those policies. To participate in the give and take of rational democratic debate I must be sensitive to evidence that would undermine my case. I must be bothered by harmful consequences of the policy that leave me untouched. In short one must be both public spirited and rational.
It is here that Enlightenment distrust of religion skews the picture. There are a significant number of people who think that religious belief is inherently irrational. If this were so, then religious people could only be second-class democratic citizens. Their public policy preferences would be “faith-based” and not “reason-based” and so could not be part of a rational policy debate. Facts could never cause such people to change their mind. They would be legitimately pushed to the margins. We could still allow them to vote but like children they would be unable to participate in the "reasoning together" which is the heart of democracy. In short, they are merely to be tolerated.
It is true that people on the conservative side of the Red-Blue divide often say and do things to feed this stereotype. But it is a stereotype. On average religious people are no more and no less rational than ardently secular types. The stereotype of the conservative voter is an evangelical Christian who laughs at science and evidence. The stereotype of the liberal is an arrogant snob who laughs at religion and common sense. These stereotypes feed off each other and poison the well from which we all drink.