I strongly suspect that the filmmakers exaggerated the historical violence to make their point about "Man's bestial nature" or some shit, which is funny because most of those savage Africans were played by actors with English names. By the way, how well do the black actors act? I think I remember reading that a lot of them weren't professional actors.
EDIT: Come on, no one knows what language this is? In a comm of our size devoted to languages and linguistics?
EDIT 2: New video
See 1:52 for decently long argument in the language I asked about.