I didn't see the movie; not a big movie go-er. But my Kenyan American teenage kids (15 and 18) did and had a response similar to yours, or maybe it was more, "Oh man, Mom, Nigerians are gonna be MAD about this movie. We couldn't believe that movie actually had those characters." They were really shocked by the use of an unfair stereotype when there were lots of other ways to designate a group as "evil." Even teenagers know that nationalistic stereotypes are not cool. Congrats to this film maker for adding one more layer to negative stereotypes of black Africans.