I have to agree with Beff and Demo here. Saying a gun isn't what kill you when your shot in the head is like saying I'm not killing myself when I jump off this cliff, the ground is killing me.
Quick intervention here. Massive deaths would still have occured if swords and bows were still around. We would have seen battles like in Braveheart but on much larger scales as populations boomed. And the machine gun is actually a minority, as chemical warfare and disease were largely to blame for deaths in WW1. But in WW2, yeah, machine guns rank high on the list of killers.
And I think I would rather be shot in the head than hit with an arrow or sliced apart with a rusty sword. There will always be killing, and guns are simply a more efficent, and in most cases, more merciful way of dying.
The only major bad thing about guns is that due to their wide avilability, children are more at risk with these weapons than with bows and swords, since the former requires skill to use, and the latter would be too heavy.
While it is certainly true that the gun is not the only weapon that can inflict deadly harm, there are a few major reasons that the human race would be at an advantage without them.
Guns are, fundamentally, far to easy to use. They are extremely lethal and while it does take skill to use an assault rifle, rifle, or other specialized weapon, firing a pistol from close range and killing someone is not a particularly difficult task. By contrast, stabbing someone requires that one get "up close and personal", as it were, in order to commit the deed. People who feel overly confident when holding a gun (because they are holding a gun) will not feel so confident with a knife in hand, and thus we evade such unnecessary killings.
To, guns require no skill to operate. Again, to use one well is one thing, but to simply spray bullets at an enemy (as oft happened during the World Wars), is a relatively simple matter of pressing the trigger. By contrast, a war fought with swords requires at least some skill with a blade. At any rate, confining war to blades means that (by and large) everyone has an equal chance: you cannot shoot someone from across a field, you must engage him more directly.
I imagine Telan would like that image, as it seems infinitely more "honorable" than simply shooting someone.
In all, I do think that we would be better off were the gun never invented. Yes, war would still exist, but I believe war will always exist.