After an Afghan national was charged in the shooting of two National Guardsmen in Washington, D.C., just before Thanksgiving, President Donald Trump’s administration revived his earlier calls for something that to many Americans sounded, at best, puzzling: “reverse migration.” Or, in shortened form, “remigration.” For many Black Americans, “reverse migration” describes the widespread movement back to the South after civil rights reforms undid the Jim Crow segregation laws that spurred many, including my ancestors, to move north. In this sense, reverse migration carries a connotation of social healing. Yet, as gratified as I am by how smoothly Americans of all...