For decades, Nazism and the anti-Semitism underlying it have marked zero on the Kelvin scale of villainy—the metric against which all other forms of evil are compared. This is so well understood that we now have cultural phenomena such as Godwin’s Law, the theory that online debates inevitably lead to Nazi comparisons, and the “everything I don’t like is Hitler” meme. But their existence proves the point: If one wishes to say that something is irredeemably bad, Nazis are the benchmark, the absolute.Yet recently this understanding seems to have grown less universal. Nazi symbolism and more modern versions of the...