In starting to teach national citizenship issues to 10 to 16 year olds, I always ask why they see this amendment as an important right. In the majority, having been taught to frame all questions with an individual rationalistic interpretation, they say, "Well, some people like to hunt and we should be able to hunt for food, etcetera, etcetera.
I then use the importance-explanitory clause to instill the historical necessity of the right protected by the amendment, thereby stearing them away from both the hunting weapon false utilitarian arguement and rationalistic trapping to their understanding in general.
To restate my point, what the militia was, is or should be, is not important except to explain the worth of an armed citizenry in general and from an historical perspective.
The purpose of the "militia" clause is to make explicit that the right to keep and bear arms is not about "hunting or sporting purposes".