Your data doesn't pan out, boss. Check this out: http://www.guardian.co.uk/news/datablog/2012/jul/22/gun-homicides-ownership-world-list
Sort that chart by "Rank by rate of ownership" and you'll see a problem. The US has a relatively high murder rate (compared to 1st-world countries) by firearms, and the US is #1 in gun ownership. But the problem is that Switzerland, Finland, Serbia, and Cyprus are ranked 3, 4, 5 and 6 in gun ownership - and they have very low homicide rates by firearm. The problem that data presents to you argument is that it undeniably demonstrates that gun ownership does not directly affect the murder rate. If it did, you would expect a gradual and more-or-less parallel drop in the murder rate as the gun ownership rates drop as well. But that just isn't the case.
The other interesting point this data makes is the fact that the murder rate by firearms (rate per 100,000 population) is not very high in 1st-world countries. In the US, where the rate is relatively high, less that 3 people are killed each year per 100,000. Cancer, on the other hand, causes 178.7 deaths per 100,000 people in the US ( http://seer.cancer.gov/statfacts/html/all.html
) each year. Accidents or inintentional injuries: 38.4 per 100,000 per year.
I'm not purporting to know what the cause of incidents like Newtown and Aurora is; that's beyond my abilities. But what I can say, based on hard data, is that gun ownership is not a direct cause of gun deaths, and gun deaths in the US are not high enough to warrant this kind of fanatical attention. You want to really cut down on senseless violence? Go after cancer and the other big terminal killers. Guns just aren't that big of a problem.