The actual problem with Batman's no-kill-rule is that the comics have made it into a big deal and Joker (and other villains but Joker is the repeat offender) keeps engineering these situations to try to get Batman to break it.
It's not surprising that lot of people would look at this cartoonishly evil clown who cannot be rehabilitated or contained and who will just keep coming back and go 'well maybe just kill this one clown'.
It's a hole Batman comics have dug themselves into with the repetitive storylines that usually manage to say nothing interesting.
















