Remember, even today we're still getting nonwhite actors excluded from roles they should be getting -- the main characters in The Last Airbender and Starship Troopers, Ra's al Ghul and Bane in the Batman movies, etc. There's still a lot of prejudice, a lot of executives who assume movies with nonwhite leads can't make a profit. We're far from achieving sufficient racial neutrality in Hollywood that casting white-for-black and black-for-white can be treated as equal and interchangeable choices. It would be great if we were at such a point, but we're nowhere near it.
So, what you're saying is, there would be some outrage, but ultimately, nobody cares?! So, what's the problem?
I mean, I can understand
outrage over the non-Asian cast of The Last Airbender, but with Amanda Waller, race isn't a crucial part of the character.
Also, seriously, Waller is more of a villain character, and since I already cast the main villain with Keith David, wouldn't it seem even more racist if the other villainous character of the movie was also black?!
Besides, I'd make up for it by casting CCH Pounder as the US president.