That doesn't seem to make sense. All that would do is to make sure that a nut job knows how to properly shoot the gun. Basically what you are saying is "a Swiss wouldn't have missed Trump".
The difference might be in what guns mean to Swiss people vs. the US.
A gun in the US has this "if the government becomes destructive of these ends we can start shooting" connotation. A gun is there for self defense. Someone doesn't get off your law, you use your gun.
In Switzerland the gun and the compulsory military service you mention is there for the people to protect their country and fellow countrymen. You are trained in defending your neighbor, who just stepped on your lawn against outside aggressors.