I don't understand your question. The long term value I'm talking about is that of the system being gone, so it being gone is a realization of that value, not a point that the value isn't there.

That's like saying "What is the value in winning the lottery if I already have all the lottery money in the bank."

>If anything the fact that some slavers where more personable means more people can conceive of such a system showing up again which will help avoid it.

Or alternatively, it could convince people that slavery is not that bad. (Which is exactly the point he was making.) And now we're just betting on which is more likely: that nice slave owners will teach us that the evils of slavery can be hidden, or that they'll convince us slavery is not bad.

But those are the same thing. The way you hide the evil of slavery is by convincing people that it is deserved and just. You say "We don't need to pay our employees more, because they are not Titans of Industry like us, they are Welfare Leeches." His point was that you can fix it faster if it is obviously evil, and that is better than living for centuries in a society that doesn't value you.