I think the "Batman should have killed the Joker" theory is a canard. As noted on that recent thread, if Batman kills the Joker, just because he MIGHT escape Arkham, that makes Batman a murderer.
Where the writers go wrong is that Batman should have killed someone in self defense.
I remember about twenty years ago, they seemed to be starting to accept this.
There was a scene in a 'Tec story (Barr and Davis) that had Batman beseiged by machine gun toting terrorists and Batman grabbed one without comment, spun him around and used him as a shield when another fired. Very brief, very cool and not mentioned (so O'Neill probably missed it).
In "Cosmic Odyssey," Batman grabbed a ray gun dropped by one of Darkseid's parademons, and used it to blast a basketball sized hole right through the parademon (while thinking/narrating "I don't like guns, but sometimes you have to go with the tools you have.")
And, about the same time, during the Collins/Starlin run on Batman, there was a conversation where Batman admitted to Jason he'd killed people, "but only in self defense."
Shortly thereafter, however, O'Neill must have woken up from his nap and realized he'd violated his own "Bat Canon" because it was after that we got a ton of the "Batman doesn't kill" "Batman hates guns" comments beating us over the head.
Basically, I think the "BB" writer had it correct "I won't kill you, but I don't have to save you" is how Batman should be portrayed.
