I didn't say it was an "unalloyed good." I said that our prosperity is the product of that system. So are many of the bad things about America! Funnily enough, the immigrants who are eager to write themselves into the story of American prosperity never seem to want to take credit for all bad things about America...
I also think you're missing the forest for the trees. You can find many cultures that enslaved people. The Arabs were trading African and European slaves for a thousand years before Europeans showed up to booming slave markets Africans themselves had built. But you can't find any culture that undertook large-scale worldwide efforts to end slavery, or any one that killed hundreds of thousands of their co-ethnics to end slavery for other people. Are you aware of any other society that has done that?
I also think you're missing the forest for the trees. You can find many cultures that enslaved people. The Arabs were trading African and European slaves for a thousand years before Europeans showed up to booming slave markets Africans themselves had built. But you can't find any culture that undertook large-scale worldwide efforts to end slavery, or any one that killed hundreds of thousands of their co-ethnics to end slavery for other people. Are you aware of any other society that has done that?