I think that interpretation would fall apart on the understanding that women and children were also allowed to own firearms. Slaves obviously weren’t, but they were legally defined as 3/5 of a person at the time (for unrelated reasons).
Cool...slaves could own 3/5ths of a gun...leave off the trigger and the barrel.
I'm sure they were allowed. It's also quite possible that their right to own them was protected by their state constitution.
But we're discussing who the second amendment protects, and it protects "the people". "The people" did not include women and children.
As an example, Article I, Section 2 of the U.S. Constitution reads that "the people" elect House representatives -- women and children didn't vote back then.
All that's different today, of course. "The people" now include women and non-whites, and the military/militia is not the same.
Because of that, it's easier to examine the relationship between those who comprised "the people" in 1792 and those who comprised the Militia in 1792. Turns out they were the same individuals.