Why is it rational to love my enemies?

Matthew 5:44 KJV >But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; In Buddhism, it is taught that you should love your enemies because, at some time in the infinite sequence of rebirths, it was certainly the case that your enemy was once your mother. Therefore, hating your enemy is as irrational as hating your mother. This isn't a true explanation, but it is a rational justification for loving your enemies. But in Christianity, everyone is an atom created by the Creator, completely detached from everyone else. In light of this, **why is it rational to love your enemies?**