The thoughtless cruelty of that last line is heartbreaking:
They will be sold either separately or together, as may suit the purchaser.
Like a plot of land which the seller is prepared to subdivide! John Kennedy, whoever he was, clearly thought of this whole business as no more fraught than a land sale - because it was, after all, a property transaction.
How could an apparently pious people get something so morally fundamental so wrong? In The Civil War As A Theological Problem, evangelical historian Mark Noll argues that when Americans turned to the Bible for guidance on this issue, their hermeneutic did not allow them to receive a clear answer. The "trumpet gave an uncertain sound" (I Corinthians 14:8) and, precisely for that reason, Americans "prepared themselves for battle".
I don't have any edifying conclusion here. I reflect on the anonymous, exploited slaves - and on John Kennedy, ignorantly taking part in great wickedness - and I wonder what it is that I am blind to, today.