That's an academic way of looking at it. A more practical way is to say that without the gun no one could shoot someone. Now, even that is incorrect when you look at it. Pick the low hanging fruit first. Go after the guns that do the most damage such as assault rifles, weapons with large clips/magazines, automatics, hidden guns.
I agree that banning certain weapons would help, but again, no amount of legislation will make a larger impact until we change as a society.