As ever in this age of Donald Trump, politicians and journalists are reducing the violence in Charlottesville, Virginia, on Saturday to a debate over Mr. Trump’s words and intentions. That’s a mistake no matter what you think of the President, because the larger poison driving events like those in Virginia is identity politics and it won’t go away when Mr. Trump inevitably does.

The particular pathology on display in Virginia was the white nationalist movement led today by the likes of Richard Spencer, David Duke and Brad...