Fact: Beck and his idiot guests are representative of all gun owners in the US.
As long as we are throwing around anecdotes, here is a case of a principal stopping a school shooting with his own gun:
The NRA generally does a terrible job speaking out for gun rights, and their handling of the tragedy in Newtown was extremely poorly handled. That said, they are right when they say that the only way to stop a bad guy with a gun is a good guy with a gun. It's so obvious it sounds dumb, but it's true. Why would you call the cops in response to a shooting? They are the good guys and they have guns. Any talk by somebody like Beck or his guests about armed kids is purely idiotic, but it doesn't change the fact that force must be met with force.
Yes, Lanza killed himself, as most spree shooters do (there are a few notable exceptions however). They generally do so when confronted by the reality of law enforcement closing in, which is what happened in VA Tech. But the sooner you can meet the shooter with an opposing force, the sooner you can bring the situation to an end, likely saving lives. Saying that Lanza killed himself so there is no point in considering ways to stop him sooner is a stupid response to a stupid point from Beck.