You can not be more wrong. I've discussed this issue with flat-out leftist gun-grabbers and they are using the same exact argument as you.
Then there is always the explicit reason given in the amendment for its being there: " A well regulated militia, being necessary to the security of a free state
Notice that they included the term "free state". If the crap ever hits the fan, the founders intended for citizens to be armed similarly to the military. Alexander Hamilton writes in the Federalist Papers...
"This will not only lessen the call for military establishments, but if circumstances should at any time oblige the government to form an army of any magnitude that army can never be formidable to the liberties of the people while there is a large body of citizens, little if at all inferior to them in discipline and the use of arms, who stand ready to defend their own rights and those of their fellow-citizens."
Gee after you tell me I am wrong I guess I will just give up. After all who could resist such persuasion?
In Hamilton's day the difference in weaponry available to private individuals and the military was miniscule compared to that of today. Now the military has aircraft carriers and submarines with gigantic firepower, chemical weapons, biological weapons, nuclear weapons. Individuals will NEVER be allowed to own these. His argument has been invalidated by technological advances. The only way the US military could be resisted by the citizens would be if it refused to fight them.
Nostalgia is ok in its place but has no bearing when considering policy.