It isn't an opinion. It's as scientific as it gets.
Your post is opinion, there's some pseudo-science within your post but ultimately it is a biased opinion. By following your statistical analysis above by considering only two factors: rise in gun ownership and falling violent crime figures, you are coming to a very short sighted conclusion. There are many other arguments out there which could have been a larger contributing factor than more gun ownership such as outreach programs, changes in judicial sentencing, changes in public perception to specific factors of violent crime, heck even the BBC published an article on how removing lead from petroleum/gasoline in our cars has a strong correlation with reduced figures in violent crime.
I'm not educated enough in social policy to comment on what changes in society would have had an impact on violent crime levels but you can't state that guns do not cause crime from the figures mentioned previously. Causation of crime comes in many forms, some that we understand and some we are yet to discover. For all we know other factors may have been more influential in reducing crime during that period than the impact of guns in circulation on increasing crime.
You also have to consider that many crimes wouldn't exist or wouldn't be so accessible if it weren't for gun ownership such as school shootings [1] , armed robberies [2] and homicide [3] .
I'm neither pro- nor anti- gun ownership, I live in a country without firearms and that's fine by me. I do see merit in firearm ownership when regulated properly to the extent where any person who has taken a test in firearm safety, is of a stable mind and hasn't committed a violent crime [4] in the last 5-10 years can own a firearm but this I will tolerate only with strong regulation.
---
[1] How else would you go on a rampage in schools or other buildings? Sure you could use a knife, sword, axe or whatever else you choose but ultimately your attack range is gonna be a lot less allowing a lot more people to escape unharmed and a lot easier for people to overpower you if they so dare.
[2] I mean armed in the sense of being with a firearm. A quarter of robberies of commercial premises in the U.S. are committed with guns. Fatalities are three times as likely in robberies committed with guns than where other, or no, weapons are used.
[3] In the U.S. in 2011, 67% of homicide victims were killed by a gun. There is little doubt that many of these victims would have been murdered if there no were no guns about since those who have the intention to do so and have planned it will do it without firearms. However having ready access to a gun for an enraged, unstable individual wanting to harm another because of a form of dispute is definitely going to have an impact on crimes which weren't planned.
[4] Obviously murders, attempted murders, brutal assaults and the like will prevent them ever owning a firearm and the time frame can be varied depending on the severity of the crime.