And what story reason is that? That it takes place in Africa? Hey, it's fiction remember?
The story reason is because his nation is based on a real time in African history and they isolated themselves from the rest of the world, there were no white people in their nation at any point, and there weren't really any other black people besides who specifically was born in wakanda.
Hes also black because his creators were trying to make a statement and a stance against subtle racism in the comics industry when they created him. He was not done as a fluke lol.
Ariel has NONE of that stuff.
And this is where this "fiction" argument falls flat. Apparently it's only valid if the character being changed is white.
No, its valid any time the characters story or history isn't based on any real setting and so can fluctuate.
That being said, there is also the fact that many minorities are under represented in film and movies, and so they are not on equal playing fields as some would suggest. Would you say a person in a wheelchair getting a head start in a race against someone with two legs was unfair for the person with legs?
Because of this, when a minorith character is made white(and this has happened a ton of times and still does) they are actually taking away a role that could have gone to a minority but didn't and this is usually for racist reasons., which is not equivalent when the opposite takes place. Theres no shortage of white characters in popular media, after all. That doesnt mean that any white chatacter being cast as white is a bad thing either.
Many studios have a history of not wanting to fund movies that feature minorities prominently. Ridley Scott couldn't get funding to make a movie about Moses unless they cast the white British guy Christian bale. He went on record to state this is why he didn't cast Hebrew actors or Egyptians.
One of the higher uos at marvel, Ike Perlmutter almost prevented black panther from being made because he explicitly didn't think movies with minority leads made money.
If you do research you'll find plenty of similar stories. So when you see a white person playing a minority role, it's probably because of racist tradition in Hollywood. When you see a black person playing a role that maybe could he white but doesn't have to be, its not the same. If a person is in a role where race is incidental, and the best person for that role happens to be a minority, it would be pretty messed up to not hire them just because of their skin color.