I don't think that whole controversy is about what you think it is. Consider the number of google hits on this search: https://www.google.com/search?channel=fs&q=robert+downey+jr+... (about 9130) to this one: https://www.google.com/search?channel=fs&btnG=Search&q=zoe+s... (over 2.1 million)
Why is it worse for a light skinned woman to play a darker-skinned woman than for a white man to play a black man?