On April 15, a pro-Trump, pro-free-speech rally at University of California, Berkeley, descended into violent mayhem after radical far-leftists — members of the organization Antifa — began to attack the peacefully assembled crowd. Antifa, which stands for “anti-fascist action,” is a network of loosely affiliated far-left anarchist and communist groups that orchestrate violent protests and attacks on populists, conservatives, and anyone else its members deem to be “fascists” or “Nazis.” “Anyone who tries to hold any sort of right-wing event literally gets beat up by militant communists in the street.” Antifa was formed originally in Germany in the 1980s, its...