I think it is a kind of self-protection, though probably an unhealthy form. If I still feel as though I like or love the person, I would still want them actively in my life and sometimes for one reason or another that's impossible. It's a way of detaching and moving on. Unfortunately I don't handle well the idea of keeping the good memories although the friendship or relationship didn't work out. It's too painful. So, the dislike/hate becomes a waystation on the way to eventual indifference, which is also kind of sad, but ultimately it feels like blessed relief.