Let's see, if it was really about racist people not wanting black people in videogames, well, we would have this thread for every videogame where there is a black guy. Do we have it? No. Ok, so probably not that.
What is it then?
Well maybe it's that people cares about the lore in their games. If you are setting a game in Norse mythology, by default you'll expect the pantheon to look white. Now of course, this is fantasy, the game creators can do whatever with their game, yes we all know and acknowledge that, yes Kratos is a fictional character they inserted in Greek mythology and now into Norse mythology, yes. But, there's an explanation for that in the previous games, and we buy it. So, instead of tweetting bs and calling people racist, I think it would be better if you go ahead and tell your audience that cares about your game, your lore and your franchise, why is this, how this character ended up here, maybe comes from another mythology just like Kratos, maybe whatever, you are the writer, if your story is decent maybe people will buy it (or at least say there will be one). Otherwise, people sees this and rolls their eyes because it just looks like an empty attempt to pander to the American public with your American view of what diversity is. People are not saying what the hell is this because the character is black, but because a priori it just doesn't fit the setting, in the same way as if I play a game with a 14th century Inca setting and their god looks Russian, even if I'm an Inca boy riding a flying unicorn llama in a fantasy world, the Russian looking god will look kinda out of place in the narrative and the writers better explain why is this.