You can kill people much more quickly without a gun. Guns are irrelevant. You can use them to protect or to kill. When it comes down to things such as 9/11, you can't protect yourself with a plane. You can kill people with one though, at a rate much higher than with a gun. Same with cars. Guns can be used for many things, and terrorists use other methods that don't require guns that are always more dangerous and fatal.