South Park

"So?" is how I feel about fictional characters being cast as different races in and of itself. If it's done in a pandery way and/or the piece of media is a turd, that's different, of course.

But, for example, the Hannibal TV Series is hands down the best part of the Hannibal Lector IP. They made Jack Crawford a black guy after he was white in all previous incarnations. But Laurence Fishburne killed it in that role. His portrayal of Jack was the best yet.

They also made Freddy Lounds a woman, but it was also done well enough and worked for the story, even if Philip Seymour Hoffman is a better actor. It certainly didn't detract from things at all, though.

Your complaint should go deeper than "this person was this way in this portrayal and this way in another." Both "this is just pandering in a way that makes the story worse" and "this is a historical drama portraying history inaccurately" are good reasons.