The killer was a white guy, a Christian by birth if not belief. He was not radical, just a crazed man given the means by the gun lobby to terrorize innocent concertgoers in Las Vegas on Sunday night, shooting to death 59 of them. Stephen C. Paddock was, by all accounts so far, an ordinary American. That is what most terrifies the right. And so, some on the far right have convinced themselves that Paddock could not be what he seems, what the authorities say he is. They say facts—alternative facts, perhaps—will inevitably reveal the truth, even as mainstream media...