No issues with comics, I just am one of those poor bastards that can't suspend disbelief enough to get over Batman's reluctance to kill the Joker... I think even Mr. Spock would have done it (but I can't find an image of Spock killing the Joker. If someone wants to make one, that would be awesome).
I mean I think it's kinda dumb too, but then look at the picture you linked and how a single cold-blooded murder very quickly turns Superman from a paragon of virtue into a remorseless tyrannical villain. A Batman who takes a life rapidly becomes a Batman who just murders everyone who crosses him, he is a mentally broken nutjob and that one rule is really all that keeps him from being a villain.