I hope I'm not making a straw man here, but I think your argument is that people who are going to resort to violence will find a way, even if they don't have a gun.
The thing that always gets glossed over in this argument is how much damage you can do with various weapons.
Yes, there are people prone to violence for various reasons. And yes, people, do get beat with pipes, or stabbed (both big SF news stories lately.)
But you can kill much much more efficiently with a gun. So those prone to violence, with access to guns are able to do much more damage much more quickly and easily.