Christopher Rufo took six months to contradict his own advice. In February, the conservative activist wrote that social-media posts “should no longer be grounds for automatic social and professional annihilation.” This view won’t come as a surprise to anyone who has followed Rufo’s long crusade against left-wing cancel culture. By August, however, he had emulated his enemies, arousing outrage over a journalist’s old tweets. The episode demonstrates not just his own hypocrisy but also why campaigns against unwelcome speech should always be resisted. Rufo’s about-face reveals something else too: The rules of the culture war are changing. Take it from...