You are wrong here, good sir. Here is a passage from author John Ross (emphasis mine):
"the Founders discussed this very issue - it's in the Federalist Papers. They wanted the citizens to have the same guns as were the issue weapons of soldiers in a modern infantry. Soldiers in 1776 were each issued muskets, but not the large field pieces with exploding shells. In 1996, soldiers are issued M16s, M249s, etc. but not howitzers and atomic bombs. Furthermore, according to your logic, the laws governing freedom of the press are only valid for newspapers whose presses are hand-operated and use fixed type. After all, no one in 1776 foresaw offset printing or electricity, let alone TV and satellite transmission."
You are correct about the incredible level of industrialized slaughter that a modern military such as our own possesses. From my own stint as a USN Medical Corpsman with the Marines, it is safe to say that any unit given orders to attack American citizens would instantly lose unit cohesion. They wouldn't "not fight", they'd tear each other apart. Something the brass knows full well, rest assured. Free societies are troublesome that way.
Oh, I have no fear of the US military acting against our citizens. It is of interest in this discussion that IT strictly controls the possession of its firearms. When my son goes onto his nuclear submarine he is not allowed to take a gun with him.
BTW your quotation does not refute what I said. While there was some difference in earlier times it just pales in comparison to that of today as I said. And militias often had their own artillary even privately formed militias. Private vessels also could be heavily armed.
And the newspaper analogy is not very convincing. Though it is true that even the First amendment is not and Absolute either and papers can be legally and legitimately shut down or censored in time of war. As can the right of assembly.