Hating isn't just not liking someone/something, it's a word to describe a feeling of disgust towards that someone/something.
People often say it when upset.
Cheyenne: Uhg. I hate this class so much!
Alyssa: Yes! Me too!
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Cheyenne: I hate you! You're so annoying!
Alyssa: Ow. Your words really hurt me!