Tribalism

It is practically first principles in the study of group identity that when we identify with a sports team, religious group, or political party, our self-esteem is bound up with that group. As psychologist Jonathan Haidt has famously shown, our group allegiances take on a deeply moral element. We naturally tend to associate our group and its values with moral goodness and our competition with moral depravity.

For Republicans (and Democrats), admitting that fascists and Nazis are on their side of the ideological spectrum—that they have any overlapping worldviews, values, or tactics with “us”—is a tribal psychology no-no. Fascists and Nazis, the exemplars of political evil, must share space with our partisan opponents. It works like a syllogism. Leftists are the bad guys. Fascists and Nazis are also bad guys. So fascists and Nazis are leftists.