I had heard that "Bantu" was no longer considered acceptable because it was a term coined by white settlers who could not exactly understand African languages. I looked quite extensively, and couldn't find andything to verify that it was considered insulting.
The Encyclopedia Britannica uses the word to describe both the language and peoples of southern Africa. Maybe it's just a small group that has declared the term objectionable. It seems that nowadays, you can't open your mouth without offending somebody.

In my view, nothing is completely pure and unblemished in its evolution - and especially language. Therefore, perhaps we need to learn not to be too fussy, lest we end up living in a sterile, homogenized world with no diversity and nothing at all that's interesting.

-Joe Offer-