Some progressives will do anything to avoid confronting the realities of why Hillary Clinton lost the election, and one diversion is the complaint about fake news, which is provoking even worse responses. Facebook announced this week that the social-media platform will weed out some stories, and that the company will deputize “fact-checkers” to decide if an article is credible. What could go wrong?

Facebook says it is testing technology so that a story shared on its site that is flagged by users, among unknown other indicators,...