“No one is born hating another person because of the colour of his skin, or his background, or his religion. People must learn to hate, and if they can learn to hate, they can be taught to love, for love comes more naturally to the human heart than its opposite.”

Source: She's Come Undone

Source: Love, Stargirl

Source: The Hiding Place: The Triumphant True Story of Corrie Ten Boom

Source: , said the shotgun to the head.

Source: Into the Gauntlet

Source: The Boy Crisis (2018), pp. 32.

Der Mensch der Erkenntniss muss nicht nur seine Feinde lieben, er muss auch seine Freunde hassen können.
Foreword, in the Oscar Levy authorized translation.
Variant translations:
The man of knowledge must be able not only to love his enemies but also to hate his friends.
Ecce Homo (1888)

1950s, Loving Your Enemies (Christmas 1957)
Context: Another reason why we must love our enemies is that hate scars the soul and distorts the personality. Mindful that hate is an evil and dangerous force, we too often think of what it does to the person hated. This is understandable, for hate bring irreparable damage to its victims. We have seen its ugly consequences in the ignominious deaths brought to six million Jews by a hate-obsessed madman named Hitler, in the unspeakable violence inflicted upon Negroes by blood-thirsty mobs, in the dark horrors of war, and in the terrible indignities and injustices perpetrated against millions of God's children by unconscionable oppressors.
But there is another side which we must never overlook. Hate is just as injurious to the person who hates. Like an unchecked cancer, hate corrodes the personality and eats away its vital unity. Hate destroys a man's sense of values and his objectivity. It causes him to describe the beautiful as ugly and the ugly as beautiful, and to confuse the true with the false and the false with the true.