They're not targeting people who make "dumb mistakes." They're targeting people who are trying to smuggle guns into the country. Locking someone up like this doesn't deter criminals at all.
Hey, BB, while I think (from more than one personal experience) that Canadian border patrol folks are cork-soakers, what does the law say that leads you to believe that it's targeted specifically at gun smugglers?
Unless the way the law is written makes a distinction between intentionally and unintentionally bringing the gun into Canada, I'd say it's targeted at those who'd unlawfully bring guns into Canada. Period.
That being said, I think that if the guy definitely brought his gun by accident, he shouldn't have to pay as much of a price as some gun smuggler.