" What don't the small-dick gun-nuts understand about that straightforward fact?"

What YOU don't understand is that they DO understand that! Their common 'reasoning' is that because there are already so many guns around...especially among their peers... they think their odds are better if they also have guns. It's a smaller version of the arms race among countries.
Once many peers in certain cultural communities have guns, it becomes a standard way to settle disputes that were once settled by fights. I once read an interview with a kid who had been convicted of a shooting. He just shrugged and explained that having a gun was a quick way to solve a problem-- and you didn't have to be BIG or get beat on (if you were smart & lucky). ... and if you wanted to compete in the drug business, or to rob & steal... a gun became the only way to be...ummm.. efficient at it.
   Yes... it's a circular argument. The more that others have guns, the more that 'they' feel they need guns.
   The same general reasoning is used by the 2nd amendment crowd who "don't trust the government". Why don't they trust the government? Why... because the government is secretly scheming to take away their guns! (It's more complicated than that, but you hear that constantly from the 'Militias'.)
And once so many bad guys...of various types... have guns, many good guys succumb to the idea that they need to 'defend themselves and their families'.....and there are now approximately 4 million AK-47s in private hands in this country. You all wanta come over here and help me take 'em away?

I once knew a guy who carried a .45 and thought he was being "good guy with a gun". We debated everything about weapons- and I once said (tongue in cheek) that I thought we ought to solve the horrors of war by issuing all soldiers a bag of marshmallows which they would throw at each other till one had a certain number of 'hits'... and they were then 'out'... winner was last one standing.
   My friend looked thoughtful for a few seconds, then said: "Yeah... that might be ok for awhile... but then some bastard like ME would come along and put a rock inside each marshmallow, and off we'd go again!"

   He made a certain amount of sense.

Guns ARE a stupid, horrible way to deal with life.... but once they reach critical mass, the common human mindset often kicks in that "I'd better be prepared". There are many arguments against that sort of reasoning, but the NRA and their $$$$$$ promote it constantly, and Congress runs on $$$$ from lobbyists.

Right now, the BEST we can hope for is small gains in background checks and campaigns by those of us who remain semi-sane to pass step-by-step laws to curtail ammunition sales and the worse types of guns.............we are banging small rocks at anyone who will listen.