K_Michael,
Boo hoo, they made a fictional character black. Sure, the original story was Danish or whatever, but mermaids definitionally don't live in Denmark, so they can be whatever ethnicity or mix of ethnicities the creators want.
For the record, I agree with you that mermaids are not inherently white, and they can be acted by anyone of any race/ethnic background. The problem I (and others) have is the fact that they blackwashed Ariel, a character made white with the Disney cartoon. If diversity was absolutely necessary, then the obvious solution would have been to create an absolutely new story featuring a mermaid played by a black actress.
Its like complaining about having black Vulcans in Star Trek. There is no heritage or truth that's being "whitewashed" or "blackwashed."
No, it is not. Any alien race can be played by anyone. Leonard Nimoy and Mark Lenard were not the entirety of the Vulcan race. But whomever plays either role must be white. To do otherwise would really piss fans off because it would be a purposeful washing mischaracterization of the firmly established character.
Personally, I don't care either way. When Idris Elba was cast as Heimdall, I thought it was cool because Idris Elba is cool.
I could care less too, since it was a fictional superhero movie.
When they cast Johnny Depp as Tanto, I thought it was fine because I like Johnny Depp as an actor.
That movie was obviously was a spoof on The Lone Ranger, making Tanto a goof ball like no other than Johnny Depp could play it.
By comparison, the whitewashing of historical figures such as Jesus Christ is a lot more sinister, to the point that some Christians have used the claim that dark skin is the mark of Cain and/or the curse of Ham as a justification of the slave trade and white supremacy, while ignoring the fact that Jesus was Middle Eastern.
Christ was not "whitewashed." Since Christianity was dominated by mostly Caucasians, Christ reflected that image.