Certainly an interesting point, and one which I am well aware of. Being a German citizen as well as Canadian i was almost sent to Rekrutenschule for mandatory 2 year enlistment. Similar to Switzerland all Germans are required to go (not keep the guns after thou).
While I certainly cant say for sure why switzerland doesn't have as high a level of gun violence I can say that its a night and day different culture. They have no military, and being a neutral country do not partake in any military conflicts what so ever. Violence, settling things with guns and military arsenal is simply not in them. Another thing to consider is that like the members of the US military they are properly trained to use and respect fire arms. I'd be interested to see, but id venture a guess that the number of military personal in the US that commit gun crimes is probably proportionately lower then civilians? Just a guess.
Id say its more to do with their culture of not buying guns to protect themselfs from other gun owners.