Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that. Hate multiplies hate, violence multiplies violence, and toughness multiplies toughness in a descending spiral of destruction. So when Jesus says “Love your enemies,” he is setting forth a profound and ultimately inescapable admonition. Have we not come to such an impasse in the modern world that we must love our enemies– or else? The chain reaction of evil–hate begetting hate, wars producing wars–must be broken, or we shall be plunged into the dark abyss of annihilation.
Quoted from page 53 of the 1963 book The Strength to Love in the chapter entitled “Loving Your Enemies”