Odyssey cast

Why do people get upset at the people who don't like the cast. I personally think it is stupid to cast someone in a movie about Greeks who doesn't look Mediterranean. I would also think that about a movie were it is a story which was specifically about one race if there was another race in it. If someone made a movie about, say, the Han dynasty, and there was a white guy playing the role of the Emperor or The Epic of Sundiata, if it wasn't only black people I'd think it's stupid. If you're gonna make a movie with any historical background, then make it accurate. I know some people would just say hey why does it matter? Will it affect your viewing, and yes, for me, and I assume other's historical accuracy does affect my enjoyment of the movie. If I'm watching a high budget movie, and there is someone who shouldn't be their, and the movie doesn't explain why they are there, then yes, it does make the movie, in my opinion, less thought out and worse. I'm sure their are just racist people out there, and the only reason they care is because she's not white, and they don't actually care about the accuracy, but then get mad at them for being racist, and don't get mad at people who specifically just don't like it because it's inaccurate. If someone made a movie about Zimbabwe, and ever cast member was white, would that be a problem? If yes, then Helena being black is stupid.