Visiting Martin Luther King Jr. during the Montgomery, Alabama, bus boycott, journalist William Worthy almost sat on a loaded pistol. "Just for self-defense," King assured him. It was not the only weapon King kept for such a purpose; one of his advisors remembered the reverend's Montgomery, Alabama, home as "an arsenal." Like King, many ostensibly "nonviolent" civil rights activists embraced their constitutional right to self-protection--yet this crucial dimension of the Afro-American freedom struggle has been long ignored by history. In This Nonviolent Stuff'll Get You Killed, Charles...