As you point out, Switzerland has an overall rate of violence that is quite low, for example slightly lower than that of Germany (http://en.wikipedia.org/wiki/List_of_countries_by_intentiona...).
However, surprise, surprise, it has a "firearm-related" violence level that is 3x that of Germany, and more than 8x the gun-related homicides. Could that have anything to do with the fact that the Swiss have their Army rifles at home?
How again does Switzerland demonstrate that higher gun ownership does not correlate with higher gun mortalities?
And you say "the plural of anecdote is not data", when just before you used a single incident to "demonstrate" that tighter gun control doesn't work. Huh?
Or is this the old straw-man of "if we cannot eliminate gun violence completely, we shouldn't do anything?" Reduction is a good target.
And no, we do not need double-blind controlled experiments to (a) change regulations that affect lives and (b) actually have those regulations have a measurable positive impact.
Aviation regulations are often changed because of single incidents, when careful analysis of the factors that led to the incident leads experts in the field to the conclusion that making the change could prevent that accident.
Take the awful accident that happened in Tenerife (largest civil aviation disaster ever): one of the contributing factors was that one of the pilots heard "take-off" from ATC and thought he was cleared for take-off, when he had been told to stand by for take-off clearance.
Nowadays, the words "take-off" have been eliminated from pilot/ATC communications except for the phrase "you are cleared for take-off".
They didn't wait to have a statistically valid sample of horrendous air-crashes to make this change, a single incident and its subsequent analysis was sufficient. It is this sort of careful analysis and action that has made air-travel as ridiculously safe as it is (in fact so safe that statistical analysis is nigh impossible these days...that's a good thing).