These words were taken from Frederick Douglas’ “Fourth of July” speech. He was an African American abolitionist; the full sentence is “for revolting barbarity and shameless hypocrisy, America reigns without a rival.” He’s basically saying nobody does slavery as horribly as the United States; his other words in the same speech are “There is not a nation on the earth guilty of practices more shocking and bloody than are the people of the United States, at this very hour.”