It's pretty simple really to me anyway. Gun types will exist no matter what is done and the US does not manufacture all guns so we cannot control what happens from the moment any gun leaves an assembly floor.

Your question about dealing with thugs armed with handguns or assault rifles would be ideal but the reality of this world is simple and the history of it is as such.

Militaries make weapons.
Militaries make more weapons.
previous generation of weapons go to public hands.

I understand your point of view but the idea of it is not reality. A weapon is a weapon is a weapon. Even if there were no firearms in existence and the world was a primarily peaceful place arms races would still happen.

fists>clubs>knives>staffs>spears>swords

You can't try to make any real sense of it. Just remember that humans as a race are warlike by nature.

[Linked Image from nodiatis.com]