since the constitutional 'we, the people' are no longer the well-regulated militia. The 2nd was a protection from standing armies, a matter we people clearly no longer worry about (as our standing armies are huge).
It is also hard to point to the Miller decision: "The Court cannot take judicial notice that a shotgun having a barrel less than 18 inches long has today any reasonable relation to the preservation or efficiency of a well regulated militia, and therefore cannot say that the Second Amendment guarantees to the citizen the right to keep and bear such a weapon." and then next state "I believe military-style assault weapons will never be protected by the court in the name of the Second Amendment."
Either the 2nd protects militia-grade weapons, or it doesn't. (leaving out the whole "personal use/self-protection" notion).
Anyway, Madison knew public opinion mattered more then any restrictions put on paper:
"The restrictions however strongly marked on paper will never be regarded when opposed to the decided sense of the public; and after repeated violations in extraordinary cases, they will lose even their ordinary efficacy. ... Should an army in time of peace be gradually established in our neighbourhood by Britn: or Spain, declarations on paper would have as little effect in preventing a standing force for the public safety. The best security agst. these evils is to remove the pretext for them"
Since the primary reasons for the 2nd has changed in importance, and practice, it should be up to the people to decide how to treat its restrictions.