The argument opens like thunder from the gun controlling mind

Well, that's quite the intro paragraph.  From The illegally carried handguns are the problem by Matthew Yglesias.  

The widespread ownership of guns in the United States is the predominant reason we have so much more homicide than the developed countries of Europe and Asia. Differential availability of guns also largely explains why, inconveniently for Republicans, there is generally more murder happening in red states than in blue ones.

His argument is comprehensively wrong.  Widespread gun ownership is characteristic in all fifty state and all 3,007 counties, yet homicide rates vary hugely.  Partly this is driven by more or less effective governance in each jurisdiction and partly it is driven by hugely different cultural norms in the different locations.

Asian Americans have a very low rate of homicide, White Americans have a low rate, and African-Americans have a very high rate of homicide.  

Since they all have access to the widespread ownership of guns referenced by Yglesias but they have orders of magnitude differences in homicide rates, it cannot be that widespread gun ownership is the causal variable of the differences in homicide rates.  Cultural norms and jurisdictional effectiveness are the clear candidates, despite Yglesias's desire to control guns.