Symbolism, Imagery, Allegory
We know from Molly's lament, "Roth Edmonds sold my Benjamin," that she believes Samuel was sacrificed because Roth threw him off the plantation and he fell into the hands of a hostile society. Samuel's been a troublemaker from the start, a "bad seed" from the father who abandoned him, but Molly sees him as innocent as young Benjamin who was held captive in Egypt after being cut off from his family.
In the story, it's mostly the unrelated white townspeople who end up having to pay for Samuel's body. So Faulkner seems to be saying that the burdens of the legacy of slavery will have to be shouldered by all of the white people in the South.