"If you regulate guns, what about [some useful but dangerous thing that’s heavily regulated but no one wants to ban]," is the #1 dumbest argument against gun control.
#2? “Criminals don’t care about gun laws,” a formulation that produces 31,700,000 hits on Google.
This is not how gun laws work.
If someone with a criminal record goes to a federally licensed gun dealer, it doesn’t matter whether he wants to follow the law or not. The dealer, who has a strong interest in following the law because his license to operate openly depends on compliance with regulations, will run the potential purchaser through NICS. Where he’ll get denied. As has happened 700,000 times. So he doesn’t get the gun even if he wants to do this bad thing.
But if someone with a criminal record chooses to buy a gun at a show or via a private seller, they can do so because there’s no requirement for the law-abiding citizen to run the buyer through NICS. That’s why they call it a loophole.
If gun control proponents are successful in closing that loophole, people with records will have to steal guns (not that easy) or buy them on the illicit market, where they will be much more expensive because the route of gun manufacturer -> dealer -> “clean” buyer -> criminal will be that much more difficult to traverse. Making criminals pay more for weapons is good.