In California, a Black college freshman from the South is telling a story about his Latino friends from home when he is interrupted by a white classmate. “We say ‘Latinx’ here,” he recalls her saying, using a term he had not heard before, “because we respect trans people.” In Philadelphia, Emma Blackson challenges her white neighbor’s assertion that Black children misbehave in school more than others. “It’s just my implicit bias,” the neighbor offers, saying that she had recently learned the phrase. In Chicago, Kelsey O’Donnell, 31, wonders why colleagues and friends have suddenly started saying “BIPOC,” an acronym that...