Yeah, Batman's "no killing" rule is... "Oddly" treated in the movies. Especially in "Begins" where he tells Ras "I'm not going to kill you, but I don't have to save you."
Um... Yes, you do, Batman. That's sort-of what a hero who "doesn't kill" does!
In one of the Batman comics Batman actually saved a mortally wounded Joker much to the annoyance of Gordon. Batman didn't cause the wound to the Joker and the Joker's death certainly would make Batman's life easier, Gordon's life a hell of a lot easier and Gotham a degree or two safer. But Batman's moral code wouldn't allow him to not-save someone who needed saving. Even if it was the Joker.
As kind of tortured as Batman's "no killing" rule is in the Nolan trilogy, what you describe here is equally tortured on the other end - and one of the things about the no killing rule in the comics that's always strained credibility.
Batman doesn't save Joker in that story because of his extreme dedication to the preservation of all life - he saves Joker because no writer can kill off Batman's main nemesis for good. That's 85% of why the no killing rule was invented - that way all your villains stay around forever so you can have endless rematches.
So while Bruce's sloppy application of his no killing rule in the movies makes him come off as creating a neat little rationalization to feel like he has a clear conscience, his obsessive application of it in the comics does the same - except now it's, "I know you're a vicious murderer who has figured out how to beat the system over and over again, but I'm just going to put you back into the system knowing you'll kill again, but I won't take responsibility for taking you out so my moral conscience is clear, we good? Bye!"
FAR more interesting would be what no one ever does - write a Batman who deals with the fact that his means create collateral damage (Batman never seems to worry about all the cars he blows up, rooms he trashes, train tracks he destroys, knocking off whole sides of buildings, whether or not he's allowing people to die or never, ever killing anyone) up to and including deaths which he does not actively pursue, but which he knows must be inevitable so that he has to constantly balance the highest stakes of loss and gains. Much is made of Batman thinking of himself as a warrior or soldier - well, they deal with the death that must come from their actions.
Though at least Batman gives some kind of nod to a hero's attitudes towards death - unlike the Avengers movie, where the heroes are knocking off enemies right and left without blinking an eye. But they bad guys aren't human so apparently they don't count.