There's only one thing that keeps Europeans, English, or any other non-african entity from abusing Africa: power.
Morality is the heart of only a few people, who typically cannot control events. Morality is a tool for some, to be used while hypocritally abusing those being 'protected'. Morality is something that all nations throw aside if there's a buck to be made. If you're inferior and hoping morality will save you.... well, funeral directors need to make a living, too.
If you want to keep the invaders out, whether it's the American Natives, or the African Natives, you need power. The invaders simply had more technology, which translated into power. Give the natives some technology. That's the only way to keep Europe from taking over Africa. Nature (disease) protected them for a while, but then technology caught up, and whites were able to penetrate the interior. Make the natives embrace firearms and learn to manufacture them and how to use them, and they now have the power.