The shooting of a teenager in Kansas City, Mo., has added “knocking on the door while black” and “existing while black” to the list of activities that allegedly put blacks at daily risk of their lives in white supremacist America. Meanwhile, the actual configuration of interracial violence is assiduously ignored. On April 13, at around 10 p.m., 16-year-old Ralph Yarl went to the wrong address in a Kansas City residential neighborhood to pick up his younger brothers. Yarl rang the doorbell, summoning the 84-year-old homeowner, Andrew Lester, from his bed. Lester, who lived alone and who appears from photographs to...