It's one of my favourite pairings too, and I used to be in an abusive relationship myself. One of the main reasons I love it is because of how much I relate to Harley - they did an excellent job of portraying it. It shouldn't make you feel guilty; they have one of the most interesting dynamics in any fandom; liking it doesn't mean you condone abusive relationships IRL.

(staying anonymous for this as yeah... bit personal, really)