My uncle told me this once:
You become the people you hate.
He's right sometimes, I'm sure. The things we tend to hate in people--the way they treat us, the way they don't tolerate us, the way they hate us themselves--all tend to become mutual when we begin to hate.
Only, there's more than that too. Sometimes the hate can come from recognizing bits of yourself in other people. Do we think they do better than us? Envy and hate. Do we think they do just as well as us, or worse, and still get noticed? Jealousy and hate.
To fight hate, we must allow others to be themselves and we must allow ourselves to be ourselves.