Cops don’t go around killing killers–at least the honest and upright ones don’t. Rather, they are focused on apprehending those killers so that they can be tried in accordance with the laws of our nation. There’s noting inappropriate with cops using lethal force when it is warranted in the performance of their duties–but that’s a far cry from them having a “license to kill.” And every use of lethal force by law officers is meant to be investigated to make certain that it was in accordance with the regulations concerning the job. Same thing is true of soldiers; in war, it is acceptable to kill the enemy, but it is not acceptable to, for example, burn down a village of non-combatants because you think they might maybe be harboring some enemy soldiers. There are rules to living in a society, and a hero of any stripe does not put himself above those rules–that’s what villains do.The cops/soldiers kill argument is a bogus one, because it’s all about context. And Spider-Man sleeps soundly, because it’s not his fault if somebody decides to kill people–he is not responsible for the actions of anybody other than himself. For him to decide unilaterally who lives and who dies would make him just as bad as Carnage, who does exactly that.