You're looking at the wrong statistic - the number of guns Americans own has increased significantly, but today only about 32% of American households have guns present compared to close to 50% in the late 1970s[0]. The same poll found 22% of individuals owned one or more guns in 2015 compared to 31% in 1985.
So you're saying that "people who want guns" have far more guns than they used to, and yet, gun crime has decreased?!?
That's not exactly a strong argument for increased gun control.
(FWIW The statistic that is useful isn't "gun ownership" across all cultures in the US, it's within specific sub-populations. There are huge discrepancies among violent crime across different sub-populations in the US, and without breaking them out, violent crime statistics make little sense, either individually or over time.)
Slice and dice how you like. Your implication that "more guns" == "less crime" is, at best, unproven, and your citation of incorrect trends doesn't change that. Conversely, the rest of the large, highly industrialized, developed nations with liberal democracies have tight gun control laws and homicide rates a fraction of the US's.
Also, I have no idea what your "porn is to rape as guns are to murder" comparison attempts to illustrate. I don't know how to point porn at someone and..well, that's as far as that needs to go. As syllogisms go, that's pretty damned broken.
[0]http://www.cbsnews.com/news/number-of-households-with-guns-o...