My son asked me this question last night. I didn’t really have a satisfying answer for him. I thought that maybe people didnt really hate themselves but hated how they felt. (I wish I had more wisdom to give to him, but I really feel like I know less than I ever did. Humbling......)
How would you all answer this question?
Depression, or a chemical imbalance in the brain. Depression just makes you hate yourself, and judge other people (and yourself) a lot. 
Thank you for that answer.
I learned to hate myself because other people hated me. Period. You don't hate yourself when you are sitting all alone reading a book, do you? No, you go down the shame spiral when someone complains about you.
So its a projection thing? And then an agreement thing? By that I mean, you say something about me, and then I take it as ultimate truth?
I guess the reason that I had a hard time answering this question is because Im so stubborn that I wont take on anyone else’s definition of me lol. I define myself. It comes at a price though, because Im really not open to constructive criticism therefore growth is slow for me.
I would think there were be multiple reasons. I will go with the first one that popped into my mind.
An ego dare leads to an action or decision that caused the person to hate themselves.
Like if you dare someone who you know is terrified of water to jump off into the lake and they hit a rock and paralyze themselves for life.