A bread knife, a hammer, a gun and a nuclear bomb can all kill. But only the last two are specifically designed to kill. You are not and should not be allowed to own a nuclear bomb. It is a weapon of mass destruction. There are guns that are specifically designed to inflict as much mass destruction as possible and the general public should not be allowed to own them – they belong in the military.
But there are legitimate reasons to own a gun. Farmers and hunters have every right to own a long gun. Every citizen has the right to self-defense and should be allowed to own a hand gun. I know very little about guns and am not qualified to determine what particular guns should be designated as illegal, but in my opinion guns designed to inflict mass casualties should be banned.