Answer me this. How do those criminals and ne'er do wells get the guns? I guess from the beginning of the process (manufacturing) all the way to the criminal, the entire process involves none of these so-called law-abiding citizens.
Maybe every gun ever used for a violent act has been acquired from a legal owner by illegal INVOLUNTARY means. See, that's the important part. Involuntary. If every gun used for a crime were acquired through a crime, I could agree completely with your argument.
I could buy one right now, a few even, without any background check or waiting period from the original authorized licensed owner, and I bet he's not the only one in the country who cares more about the dollar than the responsibility. Yet, I can't buy a car without a title, and I can't drive it or even park it in public without registering it.