I think he just said that line to distract Ra's.
I guess I could say that my Batman hasn't fully decided to live up to the almost unfaltering nobility present in many/most of the later comics. It's important to note though, that in the comics he usually always manages to land the villain in jail, unless the villain escapes him. It works in a comic-y way; catching the villain automatically leads to the villain being found guilty and put in jail (whereas in Begins he had to supply evidence, except for Crane and his thugs, where evidence of foul play was already all around the place).
I think it somewhat contradicts Batman's genius, because certainly he would realize the futility in working the way he does, and if he does, he chooses to limit his capability of protecting the innocent. And I kinda think that, "Batman protects the innocent", is a more important axiom for the character than "Batman does not kill/Batman does not let people die."
Still, I understand what you mean. What you say has merit, and I gotta say that I'm kind of beginning to see things your way. I mean, I'd love to see Batman risk a good deal to save The Joker from certain death at one point, knowing full well how dangerous The Joker is. It mustn't be tacked on though - I want what goes on in Bruce's head to be presented well, for us to be aware of why he, say, saves The Joker. I don't think "I will not be an executioner" covers everything.
I think Two-Face would be a good turning point in Batman's career, if they go with the Bruce-Harvey-friendship angle. It has good potential to put Batman more onto the path you want him to be on. First Batman could not save his parents, innocents. Then he couldn't save Harvey, an originally innocent person who later turned bad, and even though he turned bad Batman still wants to save him. That could be the starting point of him sympathizing with the villains, perhaps he even starting to draw parallells between Harvey and The Joker - and even himself/Batman.