It hangs over American politics like a moth-bitten blanket. An old and weary narrative, it crowds out conversation and lets shopworn cheap-shots masquerade as thoughtful critiques. Yes, it’s one more marker of the bad faith and disrespect that pervade our politics, but its costs go beyond hurt feelings. Real Americans pay a price for this poisonous argument. The story in question is “the Republican war on science.” That particular phrase is the title of one 2007 book, but this story’s tentacles stretch far beyond a single volume. For years, a concerted effort has been made to intertwine scientific truth with...