i would tolerate a sympathetic joker, one that appears to be GOING crazy because of nuture; society, people, work, everything just beats him down or whatever, ONLY if the end of the movie demonstrates unequivocally that joker was ALWAYS crazy. he wasn't DRIVEN crazy, he's just pure, sociopathic insanity and always was. obviously the attempt with the film is to make a villain empathetic only to pull the rug out from under the viewer, but unless it's made perfectly clear that joker is, was, and always will be irredeemably psychotic then it's missed the entire point of the character