You would be wrong then. Why are you automatically a racist if you disagree with an artistic choice? Yes, it's ultimately their choice to make, and that's FINE. I don't like it, simple as that. Am I boycotting the show? No.
I would feel the same way if for example they made a GTA San Andreas show based on CJ and the actor was white. I don't want to watch the show and have that feeling in my brain constantly screaming "that's not Ciri, that's not CJ."
That actress could nail the character completely. It's not going to change how I feel about it.
The fact you have to make up a hypothetical because you can't think of one genuine example of either of the things I mentioned proves my point? I mean if you cared at all you could just Google whitewashing and post an article like this.
Also I didn't call you racist because you have an issue with a black woman potentially being cast as a fictional character, I called you racists because your reasoning was "Diversity for the sake of diversity" which is generally only a take that racist people have because they never have issues with racial minority roles being portrayed by white actors or all white casts.