You think there's no anger in Letter from a Birmingham Jail? Really? I think there's a barely contained (and to be clear, fully justified) rage. It's civil, yes. And it's lacking in invective, yes. But Martin Luther King Jr wasn't some smiling Buddha. He just had the rare gift of channelling his anger completely into trying to make the world better. "There comes a time when the cup of endurance runs over, and men are no longer willing to be plunged into the abyss of despair." That whole glorious paragraph wasn't written without anger behind the pen.