The argument of someone not understanding is ridiculous in the first place; it’s a means to dismiss an argument without addressing the points of it.
Anyways, the ones arguing that Batman was a killer in the comics, it’s true, but he was a murder for like one year before he became the detective and didn’t kill. Whether you like him killing people or not is irrelevant, Batman has murdered people, but for much of his history, it hasn’t been intentional, it has been purely on accident or desperation, when he has been pushed to his absolute limit, he has flirted with the idea.
I don’t like Batman killing people as it normally makes him a much stronger and likeable character, any vigilante can murder without any care in the world, but that’s what differentiates Batman from others. He doesn’t kill because he knows it is exactly the problem, and it would make him no better than your common thug. Not only that, it makes him unique.
The way Batman so willingly kills people in the movie is disheartening and it seems to be purely for shock value. I didn’t like Keaton’s Batman for the same reason, but at least you could make an argument that seeing his parent’s killer snapped him. It doesn’t make sense to me either, the man has vowed not to kill and knows first-hand what it’s like to lose loved ones, but he’ll kill just to make his self feel better? That’s pretty lame. If it’s that easy to break Batman and get him that riled up, then I don’t expect much from the future installments.
I’m pretty easy to please, but scrapping an essential quality to a character that has been seen throughout some 70+ years is rather stupid.