What is "the big lie" of the Democratic Party? That conservatives--and President Donald Trump in particular--are fascists. Nazis, even. In a typical comment, MSNBC host Rachel Maddow says the Trump era is reminiscent of "what it was like when Hitler first became chancellor."

But in fact, this audacious lie is a complete inversion of the truth. Yes, there is a fascist threat in America--but that threat is...