From Orlando Patterson's Slavery and Social Death:
"The joint rise of slavery and the cultivation of freedom was no accident. It was, as we shall see, a sociohistorical necessity. [...] Americans have never been able to explain how it came to be that the most articulate defender of their freedoms, Thomas Jefferson, and the greatest hero of their revolution and history, George Washington, both were large-scale, laregly unrepentant slaveholders. Slavery, for all who look to Enlightenment Europe and revolutionary America as the source of their most cherished political values, is not the peculiar institution but the embarrassing institution.
Our distress, however, stems from a false premise. We assume that slavery should have nothing to do with freedom; that a man who holds freedom dearly should not hold slaves without discomfort; that a culture which invented democracy or produced a Jefferson should not be based on slavery. But such an assumption is unfounded. [...] Our embarrassment stems from our ignorance of the true nature of slavery and freedom."