in the amazing spider man run by straczynski,

(SPOILER) peter beats the crap out of kingpin for sending an assasin after aunt may. he does it with his mask off to make a statement that while spider man can't kill, peter parker is ready to do it.

i thought it was pretty interesting. super hero's aren't so much a deus ex machina for whatever city they protect; they're a symbol. there's no way one guy can fix crime. but they can be symbols and change how people view the world. that's why they can't allow themselves to budge on the topic of killing or certain other virtues.

and then you have deadpool