Its about owning a farm in the middle of nowhere not slavery. It really is not that hard to understand that people have different worries back when the second amendment was written when the nearest town for protection is weeks away and not hours.
It does not matter what threat its about protecting or even if its that likely to happen. Its human nature to have things to protection youself and things you care about. Like insurance you never need it until you do but then its too late.
Think of the other side of the coin. Through history the first thing slaves are denied are weapons. And there is many countries that allow weapons at home, US, Mexico, Latin America....