Hating the Joker just because he abuses Harley makes absolutely no sense.
You do realize the guy kills people, right?! Also tortures them - both physically and mentally! And he’s done this to hundreds (if not thousands) of people! He has even murdered children! And terrorizes millions of others thanks to his antics! And he generally does this just for his own entertainment!
I’m not saying the Joker being abusive isn’t a legitimate reason to hate him. I’m just saying that if it’s the only reason, that’s kinda stupid if you ask me.
“I’m perfectly okay with him killing innocent people on a whim, but the second he hurts Harley, he’s crossed a line!”