In contrast to the "holy war" tradition of the Old Testament, in which Israelites were at times commanded to kill enemies, Jesus taught, "Love your enemies, do good to those who hate you, bless those who curse you, pray for those who mistreat you. " (Luke 6:27-28)-Gregory Boyd, The Myth of a Christian Religion, pages 97-98, 100
Note that loving our enemies, according to Jesus, entails doing them good. It is important that we understand this because there's a long and sad Church tradition, dating back to Augustine, that divorces one's loving disposition toward an enemy from one's actions. This allowed Christians to torture and kill their enemies while claiming to love them.
In reality, Jesus doesn't leave open this possibility. Just as God demonstrates his love toward us by acting in self-sacrificial ways to bless us, so we are to demonstrate our love toward even our enemies by acting in self-sacrificial ways toward them - to "bless them." By "love your enemies," Jesus meas we must do good to them. ...
Notice this: there are no exception clauses found anywhere in the New Testament's teaching about loving and doing good to enemies. Indeed, Jesus' emphasis on the indiscriminate nature of the love rules out any possible exceptions. The sun doesn't decide on whom it will and will not shine. The rain doesn't decide on whom it will and will not fall. So too, Kingdom people are forbidden to decide who will and will not receive the love and good deeds we're commanded to give.
Imagine what the world might look like if more Christians started taking the teachings of Christ more seriously...