-: For most Diaspora Africans the situation is different. It has to be shown how learning African languages can enhance their material and/or spiritual development.

If something has the ability to increase your self-worth, self-esteem, self-respect, confidence, does it not also result in an enhancement of your spirit?
As for the material, the European has maneuvered and gained access all across the African continent, scheming and ploting, while pilfering the wealth of Africa from under the noses of Africans. He doesn't need to be told that imitation is the highest form of flattery; and while he cajoles the various rulers with his knowledge of their language and customs, lack of profundity not-withstanding, he acquires access to Africa's natural resources, as Africans in the diaspora sit on their hands waiting to be lead by the noses.

This sort of access through deception has become the preferred modus operandi for the European, as the rest of the world has become more aware of his natural instinct towards brutality.

Your words however speak to one of the fundamental schisms that affect the psyche of Africans in the diaspora. We have not learned how to value anything that does not bear the European/colonial stamp of approval.