I was researching stoic philosophers on their opinion of hatred. Here's some quotes I've collected:

• Mankind is born for mutual assistance, anger for mutual ruin: the former loves society, the latter estrangement. The one loves to do good, the other to do harm; the one to help even strangers, the other to attack even its dearest friends. The one is ready even to sacrifice itself for the good of others, the other to plunge into peril provided it drags others with it. Who, then, can be more ignorant of nature than he who classes this cruel and hurtful vice as belonging to her best and most polished work? Anger, as we have said, is eager to punish; and that such a desire should exist in man’s peaceful breast is least of all according to his nature; for human life is founded on benefits and harmony and is bound together into an alliance for the common help of all, not by terror, but by love towards one another. ~ Lucius Annaeus Seneca (c. 4 BC – A.D. 65)

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• Keep this thought handy when you feel a bit of rage coming on – it isn't manly to be enraged. Rather, gentleness and civility are more human, and therefore manlier. A real person doesn't give way to anger and discontent, and such a person has strength, courage, and endurance – unlike the angry and complaining. The nearer a man comes to a calm mind, the closer he is to strength. ~ Marcus Aurelius Antoninus (121 A.D. – 180 A.D.))

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• Do you suppose that you can do the things you do now, and yet be a philosopher? Do you suppose that you can eat in the same fashion, drink in the same fashion, give way to anger and to irritation, just as you do now? ~ Epictetus (c. 55 – c. 135 AD)