Our friends on the left keep warning about the rise of political violence on the right, and we’ll join them in urging prosecution if it happens. In that spirit we trust the media establishment will denounce the severe beating that a left-wing mob gave to conservative journalist Andy Ngo in Portland, Oregon, on Saturday.

The far-right group Proud Boys and other men’s-rights activists planned a rally in downtown Portland. Left-wing groups associated with the extremist Antifa movement such as PopMob and Rose City Antifa organized...