Hillary Clinton tried to tar Donald Trump as a racist last week by associating him with the “alt-right.” Yet it is Mr. Trump who has decried the loss of black life to violent crime—and has promptly been declared biased for doing so. Whether intentionally or not, Mr. Trump has exposed the hypocrisy of the Black Lives Matter movement and its allies.

Speaking in West Bend, Wis., on Aug. 16, only days after the recent riots in Milwaukee, Mr. Trump observed that during “the last 72 hours . . . another nine were killed in Chicago...