The abolitionist John Rankin was that recognizable type, a scalding Old Testament moralist dropped into 19th century America, a place that was already a boiling pot. He was also a Presbyterian preacher, but not the type to turn the other cheek. In 1841, after a pro-slavery raiding party attempted to burn his house, he put forward a summation of his principles: "It is as much a duty to shoot the midnight assassin in his attacks as it is to pray."
John Brown, Frederick Douglass, Rankin--the U.S. produced men like that because slavery, the nation's fatal flaw, was awful enough to...