I dunno, I don't like Joker raping because it's too...common. Lots of monsters rape. Joker does stuff with pizazz. With flare. I see something that "normal" boring him. Kind of like how robbery is common (in real life and in the comics). When I see comics of Joker pairing up with Two-Face or something for a plain old museum heist or some such thing, I have a similar reaction -- that something like that is just waaay too dull for the Joker. Unless there was some big bang he could do during it, what would be the point?
I actually do sexual assault research for a living (if you can call what I get paid a living) so at some level the paragraph I wrote above really squicked me out. It's a fictional character, it's a fictional character, it's a fictional character...