One example of Diop’s shoddy work: his claim of a Paleo-African language (and culture). From here:
He completely ignored all linguistic study of African languages, constructions of proto-languages and relationships and historical linguistic methodology. Here (PDF) is a overview of African languages. According to vast majority of linguists studying Africa, Egyptian certainly was African but not in the way Diop was so certain it was. He completely ignored all linguistic study of African languages, constructions of proto-languages and relationships and historical linguistic methodology. Paleo-African (and Diop’s linguistic work in general) has even less acceptance than the Nostratic theory and is so off the map I don’t how many linguists even acknowledge it as being worthy of discussion.
Diop died before population genetics took off so he made a number of points that we know now out right have no genetic reality. From here:
L. Luca Cavalli-Sforza discusses the history of various populations this paper. Here is a map of human migrations.
I don’t think anyone has written a book “Diop: Discredited!” but the work of the majority of linguists, geneticists, and archaeologists who cover the subjects he did (many who agree that Ancient Egypt was black African) certainly don’t agree with the way he got to many of his conclusions and some of those conclusions themselves (above examples).
Why would Ehret slam Diop in that interview? He was discussing Bernal and Diop isn’t doing any research or studying Ehret’s work from the grave.
Diop, Théophile Obenga, and others were understandably reactionary to the common racist treatment of African people and history in academia (racist Carleton Coon was President of the American Association of Physical Anthropologists while Diop was doing his work), but the academic world has changed significantly (thanks in large part to people like Afrocentrists calling out academic racism) and their outdated work shouldn’t be used now as a primary source, if at all, by people interested in African history.