Good one!
The Republican party of Reagan (and also Thatcher) actually believed in science. Amazing. When there was an ozone hole, they decided to close it. Their policies were experimental and partly successful. Where there were successes, folks should build on them, and where there are failures, they should learn.
But the GoP didn't. It deified Reagan and sanctified his ideals. It ignored all qualifications, so that government is intrinsically evil and the market is always right. It abandoned science (negative eternalities, evolution, climate to name three) and so cannot lay claim to a rational foundation. It's ideology all the way down.
I'll grant you that both sides make the mistake of giving preferential status to religion. And indeed, the constitution is founded atop a pre-Darwinian notion of natural law. So neither side is truly rational.
But one side actually tries. Hence, the Dems seem interested in the development of "human rights" as a compassionate replacement of the theory of natural law. Whereas Republican ideas of morality seem to slip back to the bronze age and its herdsmen's primitive ten commandments.