post is a link to an interview in which Alan Moore again puts down the story, not the art, in his and Brian Bolland's The Killing Joke. Alan has said elsewhere that TKJ is not about anything substantial; it is only about a guy dressed as a bat fighting a guy who looks like a clown. I disagree.
TKJ is about whether one bad day would be enough to drive you or me mad. The Joker had a bad day but doesn't always remember it the same way. (Metafiction: the character has different origin stories.) He knows that Bats must have had a bad day to make him do what he does. (In fact, does the Joker ask whether it was mob killing spouse, which would be the Punisher's origin?)
The Joker does a song and dance routine (of course he does; why did no one else write this?) about why we are not obliged to be sane and even about why any response to life other than insanity would be crazy. He tries to prove his point by giving Jim Gordon a bad time but fails. Gordon tells Bats to bring the Joker in by the book. Would you or I stay sane and legal like Jim or become criminally insane and homicidal like the Joker?
A fellow comics reader said that the ending made no sense: why should Bats share a joke with the Joker? I took it to be just release of tension. (I once burst out laughing twenty four hours after a difficult situation as a teacher.)
Alan Moore has also said, I think, that his graphic fictions are unfilmable. I think that a good attempt could be made at scrupulous transference to screen but each work would have to be serialized.