That argument makes too much sense for most liberals. As a police officer, I I see countless black market guns on the street. Most guns used in "drug related" shootings in my area are what you'd call "Saturday night specials". Nothing most of us would ever consider owning. Some are stolen, but most are obtained due to their very low price. And when they get done using the gun, they don't mind getting rid of their $100 piece of crap (Usually loaded with the cheapest ammo). If they ever outlawed firearm ownership, the black market would give criminals a big advantage over everyone besides the police. And after seeing the police in action on qualification day, I rely on my training and my trusty .45 for my home defense.