"Of Course, he's not 'sane' like everyone else, but he's not 'insane,' either. He is 'super-sane' able to place himself objectively in whatever situation with the mindset of taking whatever *role* is most advantageous to his master plans. "
Well said. The Joker's madness is practically a superpower-he can do things other people would simply never think of.
Remember when he tried to patent fish? That's not evil, but it is nutty as a fruitcake.