Racism is America's original and most enduring sin, with well-known historic and contemporary markers: slavery, lynching, Jim Crow, redlining, mass incarceration, police brutality. Yet a resurgence of white racism in the twenty-first century, from white supremacist rallies in Charlottesville, Virginia, to the skyrocketing number of hate crimes being reported around the country, has also brought into sharp relief another uniquely American tradition:...