I think the author of this article says it well...
"In fact, Black English is not deficient but alternate. There is no scientific basis for judging Black English grammatical structures as faulty or unclear"
"In fact, Black English is not deficient but alternate. There is no scientific basis for judging Black English grammatical structures as faulty or unclear"
We have no problem teaching Spanish speaking students English, or even constructing entire curriculum around the idea that they are still learning English while being taught. No one involved in that is under the impression that Spanish is inferior, but they recognize that, for people living in this region of the world, English is an important language to know.
We have decided that AAVE and "standard" English are the same language, but that is very much a political decision (and far from the most absurd example of different dialects being the same language). However, weather we want to call it a foreign language or not, it is still not the same language that native speakers of standard English speak. Any any speaker of English who plans on interacting significantly with speakers of another dialect will be well served to treat the other dialect as a foreign language and study it appropriately.
You could say that of French too. The trouble is, French is very deficient when judged as English. French grammatical structures are faulty and unclear in an English-speaking environment.
Likewise for Japanese being judged as Korean. It is deficient, faulty, and unclear. The fact that it is an alternate is unimportant. Japanese is very bad Korean.
The point of a language is to communicate. If you can't communicate, you need to fix that.
It can be important to speak the prestige language if one wants to advance in society, but it's not a medical problem to speak a local dialect. Would you advise an aspiring London barrister from Yorkshire to see a therapist or watch some YouTube videos on RP?