From time to time prophetic Christian voices rise to challenge our nation's "original sin." In the twentieth century, compelled by the Spirit of God and a yearning for freedom, the African American church took the lead in heralding the effort. Like almost no other movement before or since, Christian people gave force to a social mission. And, remarkably, they did it largely through nonviolent actions. Dr. Martin Luther King Jr.'s words and historic efforts as the Moses of this civil rights movement stand out as perhaps the most significant instance of a modern Christian leader acting in a...