I think people need to relax... the Ligonians were fine... they just happened to act like tribal Africans. It's not like they were eating collard greens, fried chicken, and watermelon. In fact, what strikes me as more stereotypical, is when they have some black woman as the spokesperson for Popeye's fried chicken, and show her doin' her fried chicken thing down in good ol' New Orleans, complete with a sassy black woman southern drawl... yeah... that's not a stereotyped image, lol.
Science-fiction universes are unfortunately replete with over-generalizations... entire planets with just one type of environment (Vulcan, Tatooine, Endor, etc.), members of an alien race having the same identical hairstyle (Vulcans, Romulans, Klingons) or dressing the exact same way, etc., with little to no consideration for the variety and diversity that would come naturally. It is what it is.