The real existence of an enemy upon whom one can foist off everything evil is an enormous relief to one's conscience. You can then at least say, without hesitation, who the devil is; you are quite certain that the cause of your misfortune is outside, and not in your own attitude.
There are plenty of good reasons for fighting . . . but no good reason ever to hate without reservation, to imagine that God Almighty Himself hates with you, too. Where's evil? It's that large part of every man that wants to hate without limit, that wants to hate with God on its side.