Well they like to say that black actors faced a history of discrimination, though it's not really true for many years, is it? Hundreds of movies and tv series with black actors in prominent roles. Denzel Washington started in St Elsewheres decades ago and went on to become a major star, Will Smith is not exactly begging for parts, etc.
As for Cleopatra, they could have cast an actress of middle east origin and avoided the controversy- I'm sure there are a few of them available, but perhaps they decided they needed some publicity and chose to do something they knew would be controversial instead.