When Richard Spencer, a controversial figure of the “Alt-Right,” was punched in the face during a television interview earlier this year, the Left cheered the assault, and turned video of the attack into gleeful memes. “The only good thing that happened [at Donald Trump’s Inauguration] was when suit-owner and neo-Nazi Richard Spencer was socked in the head by the new masked hero of Gotham,” wrote Jordan Sargent at Billboard Music’s Spin.com. For a movement populated by pacifists and peaceniks, the Left’s justification of the violence against Spencer came surprisingly easy.Then, last Friday, when two protestors disrupted a disturbing production in...