It was late March, and Russian President Vladimir Putin’s invasion of Ukraine was going poorly. The Kremlin had done its best to black out Western coverage of the war domestically, as well as its reports of failed Russian advances and widespread brutality. On the Kremlin’s flagship media channel, Russia-1, came a very different, ghoulish story: from Russian-occupied Ukraine, an “exclusive” report alleging Ukrainian militants brutally raped and murdered a Ukrainian woman and disfigured her corpse. In the footage, a correspondent follows a pro-Russian separatist soldier into a school basement in Mariupol to view the corpse of a dead woman. The...