I guess playing all that Call of Duty online ain't going to prepare you to be a badman in real life.
One of the canards and driving fictions of the Gun Right is the more guns equals less crime hypothesis. While there is little to no data supporting this hypothesis, it is one more example of the magical thinking that is conservatism in contemporary America. Plus, these claims are driven by sophisticated "studies" such as Dr. John Lott's--he used math and formal modeling so the argument must be accurate and correct--which was later eviscerated as a classic example of academic fraud.
Governments spend billions of dollars on training its soldiers to be lethal killers. Despite the development of "killology," there is still no guarantee that a trained warrior will fire for direct effect at another human being. The Gun Right wants all of its members to believe that they can be the thin blue line, the person who stands in the breech, the person who does bad things in the night so that nice people can be safe, he or she who protects White Suburbia from the uncivilized predators lurking at the door and window.
The gun god wants it devotees to believe that a piece of metal and plastic can make them into a hero. As the above video, as well as this piece taking on Jeffrey Goldberg's claims that America needs more guns not less, demonstrate, a bunch of teachers, rent a cops, and other day trader types with guns are more likely to be Private Snafu than Dirty Harry.
As a helpful bonus, here David Grossman works through the psychology of killing and gun use in the BBC documentary The Truth About Killing. It is well worth watching in this post-Sandy Hook moment when the Gun Right wants to spin fictions about how a well armed school is a safe school.