Truth must also be defended, which is what groups like the league and the Southern Poverty Law Center try to do as they expose hate. To most of us, at least for now, the notion that Mr. Rich, who was fatally shot on a Washington street in 2016, was murdered by Democrats because he was leaking emails to WikiLeaks is absurd. Mr. Rich’s family, on Tuesday, filed a lawsuit against Fox News for promoting the conspiracy story.

But in the alternative universe of the alt-right, that theory was taken as truth, not because the ranks of the alt-right have found logic in such stories but because those stories feed the larger narrative of a debauched world of liberalism that needs cleansing by fire. The lies are too valuable to the larger movement.

For Jews, this is personal. Had ordinary Germans and Poles and Ukrainians and Austrians and Frenchmen not played along, had they continued to shop in Jewish establishments and visit Jewish doctors, the Final Solution may, just may, not have been quite so final. To stand up to creeping totalitarianism, we needn’t throw ourselves under the tank treads. We just need to not play the game.

And refusal to play that game can be collective. If the vinyl banners proclaiming “Remember Darfur” that once graced the front of many American synagogues could give way in a wave to “We Stand With Israel,” why can’t they now give way en masse to “We Stand Against Hate”?

Why can’t the domestic apparatus of the American Jewish Committee reconstitute itself at the request of Jewish donors and members, and the Anti-Defamation League assert itself, like the Southern Poverty Law Center, in the arena of bigotry without fear of being charged with partisanship?

In the early 1930s, as Hitler came to power, consolidated control and blamed the Communists for the Reichstag fire, the Brown Shirts of the Nazi movement clashed furiously with German Communists. The German people largely stayed silent, shunning both factions. That anarchic moment always comes to mind when I watch the black-clad, masked antifa protesters preparing for their showdowns with the khaki-wearing alt-right. Antifa cannot be allowed to represent the most vibrant form of resistance, not if the great mass of the American electorate is to join in.