I don't know about people who I "hate" but my dreams that are romantic/sexual in nature always do seem to be rather random people.
The last one I had was a dream about this woman I work with who is my friend. We had a weird fight (in real life) because we both got the impression that the other one was crushing on us. Fact is neither of us liked the other one as more than friends but there was just some weird comments here and there amongst playful flirting that got us both turned around a bit about how the other person felt. When this happened she told me she was trying to be nice and not reject me flat out like all other women do because I don't have the "parts" she feels are necessary for her to have a relationship since she is straight. About a week later I had a dream about her that was romantic although not completely sexual, more like it was working up to that point.
I feel like I had the dream because she rejected me for being trans. Although I do have to argue her point in real life of not wanting to be like all the other women who reject me, first I don't get rejected often and second only one woman other than her has ever had a problem with my being trans, and that is because that woman was a lesbian. I've never once had a straight girl comment on my lack of a penis before so it was pretty insulting, especially the way she worded it, it seemed like more of an attack and a statement mad out of anger. We've worked ->-bleeped-<- out since then and are back to being friends, I worked that one out by doing the, "You were right, I'm totally wrong," approach... she glowed for about a week and now we are best buds again lol. Amazing how that line always works even when you don't mean it.
It is weird though when you think about it, the people who I've had dreams about aren't necessarily enemies but it does seem to be that kind of situation where they have somehow recently insulted or hurt my feelings in some way. I never really connected that until some of these comments on the thread.