What satirical statement does Washington Irving make about Tom Walker and society in this excerpt from "The Devil and Tom Walker"?

He insisted that the money found through his means should be employed in his service. He proposed, therefore, that Tom should employ it in the black traffic; that is to say, that he should fit out a slave ship. This, however, Tom resolutely refused: he was bad enough in all conscience, but the Devil himself could not tempt him to turn slave-trader.