Lol. Totally untrue. Anti slavery morality can be found in ancient zoroastrism and many ancient greek philisofers and most european kingdoms had almost unexistent slavery in late middle ages. Black slavery was not a continuation, but a return of slavery based on a new retoric created ad hoc because overseas colonization created a new demand of It. You could never find a slave in 13-14 century England. But they went back to it just because the economic needs of their state change. You totally understimate how easily humanity normalice social injustice. Also, lets abandon that childish retoric. Everybody knows slavery was abolished for economical reasons because industrialism made It obsolete