Yes, the SCOTUS has been known to act in an illogical and ahistorical manner such as you suggest.
However, if one uses logic and breaks the structure of the sentence down, the composition of the militia has nothing whatsoever to do with the amendment--which addresses "the people" in its independent clause. An analogy: "A well educated elite being important to maintain our independence, the right of the people to own and read books shall not be infringed" would protect all of the people, not just the elite. Without broad ownership, the militia doesn't become possible.
Regarding historicity:
"I ask, sir, what is the militia? It is the whole people, except for a few public officials." — George Mason, in Debates in Virginia Convention on Ratification of the Constitution, Elliot, Vol. 3, June 16, 1788
Of course, that is just one of many indications that the right to keep and bear arms extends to us all.
I think it does.
Now, if it said, "A well-armed populace, being necessary to the security of a free State ...", then I could agree with you. But it doesn't. The Founders believed that a well regulated Militia was necessary to the security of a free state, and that's what they wanted to protect. Not simply a gaggle of citizens with guns.
The constitutions of many (most?) states, as well as the United States Code, Title 10, Chapter 331 state that the militia consists of practically everyone. The U.S. Code states that the militia consists of the organized and unorganized militia, with the organized part being the National Guard and Naval militia, whatever that is. All other males over 18 who are not in the organized militia are members of the unorganized militia. If the SC rules nobody can have a gun except militia members — well OK — we’re all in the militia anyway. Does the left get this?