I don't think anybody actually seriously hates one of the contestants/pros/hosts. When people say things like that, I think you have to take it in the context of the show, be it Big Brother, SCD or whatever.
With a lot of reality TV, you get very involved with the contestants very quickly. SCD, for example, is on seven days a week now, and BB has live streaming for most hours of the day so it's very easy to get caught up in it and it all moves very fast.
I say I love Anton, and I do really like him, but I don't actually love him, I don't know him. But in the context of the show, I do - he's one of my favourite pros and I enjoy watching him dance or be interviewed on ITT etc. But in the context of the show and the intensity of it (consider how harsh it can get around here sometimes, for example! Nothing compared to the BB boards, but you get what I mean - you find yourself arguing about the silliest little things because it's so intense) then it makes more sense (and that's so not the phrase I want, but eh) to say 'ooh, I love him!' than 'oh well I quite like him really he's rather nice'.
Once the season is over, people will still like who they like and not like who they don't, but it's not as...vehement, I guess? Because you're no longer spending time watching that person seven days a week, so they kind of fall off your radar if you don't like them so it's really of no concern anymore.
Anyway. Just my opinion!