I wrote the same thing too, but it was denied. Actually I think it is a better rendition than what Duo has proposed. "THE Tanzanians are eating ugali" could be as good a translation, since it would point to a group of people (coming from Tanzania) doing the action of eating at the moment of speech. The use "Tanzanians" without the article suggests a general truth and should not be in the present continuous. So, I reported it.