I've read the poem then googled the painting and studied it. I can't see anything in the painting that has anything to do with slave traders. There is a fairly accurate description

of the painting, but there's nothing intrinsic that would lead to most of the inferences

derived from the painting. Yes, the people portrayed are upper class, but how does this

portrayal make the work a statement against the evils of Nineteenth century america?

Yes, the Indians were mistreated but where is that depicted in the painting?