There does seem to be correlation there.

Did you know that 3% of gun owners own half of the guns?

https://www.theguardian.com/us-news/2016/sep/19/us-gun-ownership-survey

The background fact is that over the last decade plus, the number of permitted concealed handguns has massively increased, while the murder rate has steadily decreased.  Also, *overall* violent crime is massively lower in states with open carry permits. 

These things don't necessarily implies causation, but leaving them out makes one look hopelessly partisan -- as Mother Jones is.  Considering such facts, though, means one doesn't get to paint such a simple picture.   

It's also disingenuous to account for "gun violence" without any attempt to account for deterrent effect.  While some people cast doubt on a generalized deterrent effect (i.e. believe criminals don't consider whether their victims might be armed) there are a large number of people each year who fend off violent criminals with firearms.  That makes the MJ analysis something like a financial statement that considers only debits but not credits.  Of course, most people don't report incidents where a gun saves them from a predator, so you have to use statistics for that too. 

You're right that the MJ analysis is one sided.

I've never seen numbers of people who fend off violent criminals with firearms. 

Of by guile, pepper spray, dogs, etc.