Here are some real arguments people have levied to protest the casting choice. The facts prove they just don’t hold water.
If critics are truly worried about staying faithful to the original story, we shouldn’t gloss over the original ending where the mermaid is instructed to kill her prince, but throws the knife away in despair and dissolves into sea foam instead. Not to mention, while the 1989 Disney version has a Prince Eric with bright blue peepers, Anderson specifically described the prince as having “coal-black eyes” and “raven hair.” (Also “The Little Mermaid,” who doesn’t even have a name in the original story, isn’t real.)
Claim: Mermaids live under the sea and therefore would not have dark skin
Claim: Mermaids are a European mythological figure and therefore Ariel should be White
(Also, not all Europeans are White. Also, “The Little Mermaid” isn’t real.)
Claim: Making Ariel Black is ruining childhoods and changing the character
While Disney has produced a very famous iteration of “The Little Mermaid,” it isn’t the first, only, or universally definitive work. No one owns the concept of mermaids or what they look like. A White, red-haired animated teenager is not the only version of “The Little Mermaid” to exist.
Also — and this is very important — “The Little Mermaid” isn’t real.