The U.S. legal system’s fixation on property rights and ownership, as opposed to personal or human rights, can be identified as a cause of the informal elevation of personalities to prominence. However, the emphasis on ownership can prove a disadvantage for the simple reason that it requires external validation. That is, unlike personal attributes or talents (natural properties), which are obvious and observable, a right to material property depends on external assent and recognition. In other words, a slave, be it male or female, is not recognized as such, unless socially certified.
I suppose that is what makes slavery a societal and, in the case of the U.S., an institutional sin. Never mind that it is merely an extension of categorizing progeny as chattel.