You can’t swing a dead cat by the tail these days without hitting a liberal who thinks conservatives don’t believe in science. The liberals exaggerate, but they have a point.

Half of those who self-identify as tea partiers do not believe in global warming. And despite mounting evidence, overall GOP acceptance of climate science has fallen in recent years. Likewise, half of tea partiers don’t believe in evolution. This actually might qualify as progress: A 2007 Gallupsurvey showed 68 percent of all Republicans reject evolution.

This is pretty jarring when juxtaposed with Republicans’ frequent insistence that – as Virginia governor-elect George Allen put it in 1995 – regulatory policies should be “based on sound science.” Indeed, three of the past four GOP platforms have included passages about the need for sound science. And yet the Bush era was rife with tales about the muzzling of climatologist James Hansen, or the political appointee who edited a NASA website so it termed the Big Bang a “theory” – because to do otherwise insulted the possibility of an intelligent designer.

The disconnect ceases to be a mystery if you assume that arguments about science are really surrogates for something else. The fault lines over evolution are not merely partisan, for example. Five years ago Gallup reported that only 24 percent of those who attend church weekly accept evolution as fact. But of those who attend church rarely or never, only 26 percent take issue with evolution. That’s because for cultural conservatives, evolution is not about archaeology and genetics. As Rick Santorum put it in a radio interview several years ago, it raises questions such as: “Is there a purpose for our lives? Or are we just simply, you know, the result of chance?”

In this light, the GOP’s truculent resistance to warnings about climate change also ceases to baffle. Most of those warnings have come from the left, or sources perceived as left-wing: environmentalists, academia, the UN. And alarms about the problem usually precede demands for big-government solutions. Republicans aren’t hostile to ice core data in the abstract. But if Al Gore cites it, the right won’t believe it.

Before liberals start to feel too smug about all of this, they need to look back at the numerous instances when they, too, have rejected science for the sake of ideology.

In the 1980s, America went through big scares about disappearing farm land and the pesticide Alar. The former, ostensibly caused by sprawl and erosion, was threatening to “end U.S. food exports,” asThe Chigago Tribune put it. (Al Gore was worried about that, too.) Under environmentalist pressure, the EPA banned Alar because it supposedly could give kids tumors – never mind that it was no more carcinogenic than the apples it was sprayed on.

In the 1990s, Dow Corning was bankrupted by lawsuits over silicone-gel breast implants. Driven by Naderite interest groups and feminist dogma about “concepts of beauty,” the FDA had asked doctors to stop using such implants – despite the lack of any evidence that they presented a health risk. Subsequent findings for the Institute of Medicine, a federal court, and many others all failed to find any such evidence as well. This month the FDA began approving the implants again.

In recent years progressives also have raised alarms about genetically modified foods – “frankenfoods,” as critics call them – even though two studies by the National Academies of Sciences have found they present no danger.

Four years ago, the Natural Resources Defense Council petitioned the FDA to ban the chemical bisphenol A (BPA). This past weekend, the FDA declined to do so. But several food packaging companies already have ceased using BPA out of public-relations concerns. The FDA commissioned studies from the Pacific Northwest National Lab and its owhn National Center for Toxicological Research. Both studies failed to find any potential harm from BPA exposure.

All of these cases were driven not by scientific fact, but by liberalism’s preferred narrative: Malevolent corporations endanger health and the environment and must be stopped by robust government intervention.

Many progressives now advocate an even more extreme approach, known as the precautionary principle. According to Cass Sunstein, president Obama’s regulatory Czar, that principle “requires regulation of activities even if it cannot be shown that those activities are likely to produce significant harms.” In other words: Never mind the science, just pass the rules.

Religious conservatives are not the only one to protect their sacred cows. Just look at what happened to Larry Summers, who was forced to resign from the presidency of Harvard seven years ago. Why? Because he raised the possibility that one reason fewer women reach the upper echelons of math and science is an innate difference between the genders. Summers didn’t say he liked that explanation, or even that he believed it. He simply floated a hypothesis. Yet immediately the nation shook with the sound of 112 million minds slamming shut.

This doesn’t mean liberals are hostile to science in the abstract, either. Like conservatives, they’re happy to cite research that supports their point of view. And like conservatives, they’re eager to dispute research that does not. Neither side is really looking for the truth. What they’re looking for is ammunition.

A. Barton Hinkle is a columnist at the Richmond Times-Dispatch, where this column originally appeared.