Asita said:
I think they've actually done a decent job of justifying it with Batman in recent years. In Nolan's trilogy of films he saw firsthand what he could become with the League of Shadows: little better (at his first introduction to the League's embraced of execution) than a hitman with a - supposedly - noble cause. The idea of becoming this naturally became even more abhorrent when it was revealed that the League was perfectly content to end all the innocent lives in a city if it meant ridding the world of the corruption that same city held. A variant also pops up in Under the Red Hood where his refusal to kill the Joker is actually a major plot point, to the point that he actually gets into an argument about it during the film's climax. What's ultimately revealed in that scene is that it's not a sense of morality that prevents him from killing the Joker (which he really wants to do), but fear of what he'd become if he allowed himself to do that. (Again, climactic scene, so there are naturally some spoilers associated with it)
You see something similar in the Justice League animated series with the central heroes due to their encounter with the "Justice Lords" from an alternate universe, but Superman in particular stands out due to his fear of becoming the Justice Lord Superman becoming a prominent character trait.
Maybe it's just me, but I find it works out when viewed as a humanizing trait rather than a moral or expedient one.
This sounds good, until you run into one slight problem...
Jails are not effective in comics. For most super villains, the prison is a place to relax, to nurse your wounds, before walking out and causing more mayhem. The system is broken beyond belief, particularly in Gotham. The Joker is not insane, at least, not most of the time. Sure, he has all kinds of mental issues, but fails the fundamental condition for legal insanity, knowing the difference between right and wrong yet acting in a way that is wrong.
The Joker sometimes does not appear the difference between right and wrong, knows that his actions are illegal, yet does them anyway. Having fun doing it does not constitute insanity. Nor does fascination with plants, liking Alice in wonderland, or being part crocodile. This fact was pointed out in the VERY first comic the Joker appeared in. In the real world, the Joker would be given the death penalty for even a fraction of the crimes committed. Yet, the system keeps declaring him insane instead of bringing out the electric chair.
I will paraphrase a quote by SF Debris (because I can't remember the quote word per word) that seems to apply.
"He will continue to kill people. He cannot be reasoned with, he will not listen to force, you cannot physically restrain him. The only logical solution is to kill him."
Let the Joker live, and others will die. The law will only slow the mad clown down. The Joker cannot be stopped, will never stop. Batman's only real choice is to kill him.
The Justice Lord incident was a very particular case. Lex Luther had essentially broken Superman and the Justice League. He had killed the Flash, was about to plunge the world into nuclear war, had managed to get the public to ignore all his past crimes, and was elected
President of the United States. Lex Luther took Superman, and showed that humanity is NOT fundamentally good. Democracy had failed, humanity had failed. The Justice League felt pressured to sort out the mess Lex left the world in, so tried to force it to be better. Now, if Superman had killed Lex years earlier, when all the guy was the evil owner of a company, you really think Superman would of become a dictator?
Before you even start, yes I am aware of the Superman: TAS episode where he went evil after Lois died, but we were never given full details of the rise to power and Lex Luther could of easily been manipulating the Man of Steel.