We love, or we hate other people not for what they are, but for what we love or hate in ourselves and recognize in them.
For instance, if X has a lot of traits I also have, and most of them are the reason I like myself, I like him/her as well.
If Y has a lot of traits for which I feel bad about myself, I don’t feel comfortable around, and I might start to hate him/her.
Also, those people who don’t remind us of ourselves (in any way), remain unnoticed or – if we must have something to do with them – neutral to us.
That’s how love, hate, and indifference could be finally understood.
Their dynamics are even more interesting if seen in detail. But I’ll prefer to make it short and simple: as we change ourselves, so change our feelings toward the others. The loved might become abhorred; the hated might become indifferent; the indifferent might become the one and only. So on.