The usual argument I hear is "should just anyone be able to buy a fighter jet and tanks?" And I refer them to Secret Valley, the world's largest fleet of privately owned tanks... http://www.bloomberg.com/news/videos...4-4ec22c399def
Not decommissioned tanks, fully functioning tanks. Cannons and all... and you can rent one to drive around... AND SHOOT THE CANNON, for pretty damn cheap.
I ask them to find the law that makes it illegal for the People to own tanks... not one has gotten back to me. They have the false premise that tanks are so dangerous that it must obviously be illegal to own them already. But facts shut their argument down pretty quick and turn them into blathering screaming fools. (in my personal experience at least)
Not one has admitted to being wrong as of yet, sadly.