Is America ready for a Christian Rambo? And does it make a difference if the story of this Rambo--as opposed to the Sylvester Stallone character from the 80s--is, in fact, true? Those are the questions posed by a remarkable new movie, “Machine Gun Preacher.” The film offers a peek into a once-dark, subsequently redeemed, human heart, even as it opens a window into an ongoing horror half a world away. Ever since the days when Jesus walked the earth as a man, Christians have struggled with the question of how they themselves should live. At different times, they have come...