Oh I agree with you at least on the legal terms for restriction of weapons on such attachments. It seems rather arbitrary and easily circumvented, but I still think that the aforementioned mistake is indicative of a serious lack of knowledge of the weapon, for which there should be no excuse when dealing with something as dangerous as an assault rifle. What is your opinion on a mandatory training program for all potential private gun owners? Additionally, what is your opinion on defining and evaluating a system of quantitive assessment of lethality based on things like ease of reload, firing speed, caliber, effective range, and other such weapon characteristics, and defining a legal threshold based on said statistics? Something akin to a weighted scoring system. Arbitrary still, but at least based on an empirical approach and more easily and universally enforceable.
It's not a lack of knowledge of the weapon, its the lack of knowledge of an arbitrary, capricious set of regulations that make no logical sense.
As for a mandatory training program, I wouldn't be completely against it, but the devil is in the details. It would need to be constructed in a way where it couldn't be used by some anti gun local official to prevent access for a law abiding citizen. Paying for a training program on that scale could be an issue as well.
I don't know how you could possible come up with an objective lethality scale, as it's highly situational and wouldn't really address most of the guns that are commonly used in crimes. Cheap low caliber handguns would score really low but are responsible for the vast majority of crime in this country, while a semiauto .50 cal rifle would score off the scale, but I'm pretty sure the latter has never been used in a crime in this country.