Was the Second Amendment About Preserving Slavery?

Thom Hartmann seems to think so and he lays out a pretty convincing case at Truth Out:

If the anti-slavery folks in the North had figured out a way to disband - or even move out of the state - those southern militias, the police state of the South would collapse. And, similarly, if the North were to invite into military service the slaves of the South, then they could be emancipated, which would collapse the institution of slavery, and the southern economic and social systems, altogether.

These two possibilities worried southerners like James Monroe, George Mason (who owned over 300 slaves) and the southern Christian evangelical, Patrick Henry (who opposed slavery on principle, but also opposed freeing slaves).

Their main concern was that Article 1, Section 8 of the newly-proposed Constitution, which gave the federal government the power to raise and supervise a militia, could also allow that federal militia to subsume their state militias and change them from slavery-enforcing institutions into something that could even, one day, free the slaves.

If this is true, then, like the Three-Fifths clause, the Second Amendment has to be obsolete.