This year is the 150th anniversary of the Emancipation Proclamation. SF gives more attention to the issue of slavery than most fiction does; Heinlein alone wrote 3 books focusing on it. Butler's Kindred, Asaro's Ruby/Eube novels, Mitchell's Cloud Atlas, a lot of fantasy novels and (lightly disguised) many robot / android stories... Why do our genres consider this an important contemporary topic, when so much of our culture is in denial of both slavery's impact on who we are now, and its continued existence around the world? How does SF & F overcome that denial?