I think we're going down a rabbit hole because we're arguing two different things... I'll just suggest watching Birth of a Nation if you have the free time.
I'm guessing you're saying it is that it's an outmoded way of looking at the world, and that makes it wrong that it's used this day in age, whether it's meant to be racist or not, it just is?
But I don't see how doing the same thing as before, just changing the characters from white to black makes it racist, even if it does call an outmoded view to mind... I guess it's another one of those things where I see intent as more important than whatever random image it may conjure in someone else's mind.
I think it might tap into long-running racial stereotypes, fears, or ideas about blacks that have some people upset. I don't think that most critics automatically equated RE5 being in Africa as being racist per se, but there is a whole history of negative images of blacks in mass media (the aforementioned Birth of a Nation for starters, Tarzan movies, etc.) Minstrel shows were one of America's earliest forms of mass entertainment and their bread and butter were demeaning stereotypes that I personally feel haven't really gone away but have been repackaged. And RE5 seems, from what I've read about it, to drudge some of that stuff up.
If the RE franchise had perhaps did a better job using black or non-white characters earlier on and making them more integral to the games, and showing a variety of zombies in Africa because there are whites, Asians, etc. that live in Africa, it might have avoided this firestorm. As I said before, I would like to see more diversity among the black characters (and others too)-beyond just a sidekick. Have heroes and villains, show some complexity. As for the villains, show some smart human ones. Believe it or not, there are black/African scientists, for example. Not just a rumbling mass of black folks for the largely white audience to mow down. I don't think there has been a problem with white zombies because these games usually feature white heroes, so you get that kind of diversity.
Plus whites haven't had to contend with images of dehumanization like blacks and others have. At times there has been a tendency to lump all blacks together, esp. when one black person does something bad, and to see all black people like that. And blacks at times have been called on to answer for what another black person said or did. Whites can be individuals when they need to be, or work collectively when they want to. It's not so easy for blacks, particularly living in a majority white country, and I would contend it isn't for other non-whites. So stuff like RE5 can be a sore point because of its dehumanizing aspects.
I think that the people criticizing this game and other negative depictions have every right to. Because if they don't, it's going to continue and will get worse. And if they don't say anything, it might encourage some whites or others feel that 'these people' are really like that IMO or confirm the negative feelings some whites or others might harbor.