See Does "Ask the DM / GM" equate to "Primarily opinion based?" for an analogous question class. The question sort-of seems to think there's a single right way to run this experience, which is false. Nonetheless, the fact that it is false is useful in answering the question, by talking about both the existence of multiple options and how one would in fact go about deciding which of the options to use. The answer is "the one that best communicates what it ought to be communicating" (aka "Make it up"), and similar to questions where the answer is "consult with the person or set of people in whom you and your group have vested the authority to utilize this decision for communicative purposes" (aka "Ask your DM"), these sorts of questions aren't actually opinion based (though a question about the actual right thing to make up would be), but nevertheless are closed as opinion based due to a documented common false equivalence in the minds of our site base, and also sometimes draw bad answer floods providing without good support what should be made up, rather than that making up should occur, in which case closure is appropriate.
This particular question has not drawn any such flood. While I personally think that Sardathion's answer is bad, because it equates slavery in general with the chattel slavery of the USA in specific rather than with e.g. forced labor from prisoners of war and because history is rarely as objective as people would like to think which returns the issue to a question of picking between multiple accounts while thinking there's only one right one, nonetheless it's still fundamentally about answering the actual question--
Q:What do I do to do this thing? / A:Base it off history-- rather than a specific thing to be made up. Additionally, I, of course, think my answer avoids this problem. Since our answers are the only two answers, there appears to not even be a single bad post just giving a random opinion on what to make up.
So, in conclusion, I don't actually think it should be closed at all. If we're worried about troll answers, we can preemptively protect the question, but the question itself I don't think is primarily opinion-based.