After centuries of oftentimes bloody fights against deeply engrained white supremacist views, most Americans of goodwill today recognize that racial bias is wrong. In the early 20th century, the mayor of Baltimore could gain popular support by backing local zoning laws that divided neighborhoods by race on the grounds that Black people should be kept apart—by government fiat—to reduce harm to white people. Today virtually no one would support that type of policy. But what about class bias? Is it OK to pass exclusionary zoning laws that outlaw multifamily housing and keep poor and working-class people out of towns and...