Biological populations certainly do exist, it's just that they don't correlate well with prevailing concepts of "race". The average western African is more similar to the average European than to the average southern African.
I don't think there's more genetic diversity among Bantus than the rest of the world combined.
Not population geneticists. Africa in those cases == sub-Saharan African people, not just Bantu.
I am a layman who knows next to nothing about genetics, but a bit about Africa, and I would not consider the two peoples to be in the same race. They look completely different - which is what most laymen use to determine race, isn't it?