For me a lot of it boils down to the method of killing, and more over the perception there of. With a gun, it seems very... dispassionate, detached from the victim, where as with a sword or some other sort of close combat weapon, it's up close and personal. It's an ugly, bloody mess and you have to see the person you're killing, and frankly while neither is appealing, it seems a much harder thing to get through when you're standing right there and see just what has happened. I don't know, either way it's a horrible situation.