I'm going to have to say that's a result that's unique to Switzerland. There's a direct correlation between homicide rates and assault rates (a failed homicide being classified as an assault). For your hypothesis to be correct, the overall assault rate in Switzerland has to have remained the same or climbed, while the homicide rate decreased. Indeed Switzerland has one of the highest assault rates among OECD countries (4.0%), but one of the lowest homicide rates (0.7 per 100,000).
But since most of this criticism is directed at the U.S., how do the two rates compare in the U.S.? The U.S. has one of the highest homicide rates among OECD countries
(4.8 per 100,000 - more than double the OECD average of 2.2), but one of the lowest assault rates (1.5%, only Canada and Japan are lower, less than half the OECD average of 4.0%). (The interface is terrible - you have to hover your mouse over the little bars in the graph to see the number for each country, and the bars are inverted so a tall bar is a low number.) So while Americans kill each other a lot more, Europeans attack each other a lot more. This would appear to bear out the adage that "an armed society is a polite society." If the U.S. were to ban gun ownership, the homicide rate could decline to Canadian levels as you posit, or the assault rate could rise by 2.7x to the OECD average, or some combination of both. It's impossible to say which would be the outcome given the data.
I've been following this debate a long time, and followed with much interest what happened in Australia when they disarmed in 1997 (homicides are down
, but assaults
and sexual assaults
are up, and robberies
fluctuated a lot and are currently unchanged). I don't like nor own a gun, but I also dislike making decision purely on gut feeling rather than sound statistical data. The only conclusion I've arrived at is that the cultural norms for a country matter a whole lot more than whether or not you ban guns. Guns are mostly illegal in both Canada and Mexico, but widely available due to proximity to the U.S. Yet Canada is one of the safest OECD countries while Mexico is one of the most dangerous.
As an aside, it's interesting that the data on that site ranks the U.S. as the 3rd safest country against assault. The data was from a Gallup poll asking residents of those countries if they'd been assaulted in the past year. Other measurements of assault rate I'd seen ranked the U.S. about average among OECD countries. But those were based on police reports of assaults per 100,000. So either Americans are lying about whether they've been assaulted, or people in other OECD countries are not bothering to report assaults to the police, or police in other OECD countries are lying about how many assaults are reported to them. And no the high homicide rate in the U.S. does not affect the assault rate significantly. If all 4.8 out of 100,000 homicides failed and were classified as assaults, it would increase the assault rate by just 0.005%.