Sen. Elizabeth Warren told a town-hall audience in Jackson, Miss., Monday that “it’s time to start the national, full-blown conversation” about slavery reparations for blacks. Come again? Compensating black Americans for past oppression has been a subject of discussion for decades. The senator’s problem is that large majorities of the public have consistently opposed reparations, not that we don’t talk about it.

James Forman, a black activist, called for $500 million in reparations in 1969 and inspired a 1973 book, “The Case...