That was indeed was on the dumbest Internet comments I've ever read.
As I recall, the opposite is true, the vast majority of gun- related crimes (Including most if not all of the recent mass shootings that liberals exploit to try and push for harsher gun regulations) are committed using guns which the shooter owned illegally in the first place, usually either stolen or obtained through some kind of willing yet unlawful exchange (i.e. a drug dealer taking a gun from a customer as payment for dope).