Joker's sexual innuendo is specifically designed to break down a person's mental defences. We're all sexual beings, and we can often give into things and become aroused. If a hot woman comes over out of the blue and starts rubbing herself all over you, you're not going to push her off, are you? You'll be confused, but accepting, because it feels good.
Joker knows the human psychology just as good as Batman, and he knows how to get at you, with your own mind turned as a weapon against you. As regwec said, he's like the Devil, worse than that even.
For him, it was appropriate in Grant Morrison's Arkham Asylum story to be able to get away with the whole sexual thing with Batman and the Dr. They were both his prisoners and toys for him to play with. In the story, he's wearing women's heels....and originally, he was supposed to dress like Tim Curry in TRHPS. He was meant to be acting like a transvestite, because that's the way he decided to create himself that day.
Joker's already a flamboyant metrosexual in terms of dress and style.
Morrison decided to turn him from metrosexual to homosexual, really. Under the guise of his assexuality.
Now that, was incredibly disturbing.
But it was all done in a right circumstance.
Can it or should it be done on film? Not if you want a PG-13 movie
