Hat Tip: Andrew Sullivan. "Patrick Allitt reviews Laying Down the Sword: Why We Can’t Ignore the Bible’s Violent Verses by Philip Jenkins:"
Early figures in Christian history approached the genocidal passages in different ways. Marcion, leader of a highly influential Christian movement of the second century AD, argued that the God of the Old Testament, capricious, brutal, and violent, was the antithesis of the God of Jesus in the New Testament. His own proposed version of the Bible omitted the Old Testament completely. So, a century later, did that of Mani, founder of the Manicheans, who thought of divine history as a great battle between light and darkness and denied that the New Testament fulfilled prophecies made in the Old.
Arguing against the Marcionites and the Manicheans, some of the Church Fathers, including Origen and Augustine, denied that the genocidal passages should be taken literally. In Origen’s view they should be read metaphorically or spiritually so that the Canaanites or Amalekites were not actual groups of people, deserving of death, but the tendency to sin in every human heart, against which we should make perpetual war.