Most of Disney stories are based on fiction. Meaning that the "heritage" of the characters aren't important or integral to the stories.
For instance, the main argument of the comment Bu posted is the background of the authors. That has little to do with the story themselves.
Especially a story based entirely in fiction.
The other argument is that of the stories setting. They would have a point with that, but again, it's FICTION, nothing explicitly states the character can't have another skin color. People of all races live in every corner of this earth.
The truth is it is/was whitewashed, but it's from a time period where everything was presented as such. Even now "best" presentation of a production is seen as that which has an entire white cast.
Instead of admitting to it and owning it, there have to be excuses for why something which isn't real is presented the way it is.
BTW, you bring up the "Little Mermaid"... that's when Disney finally made the attempt to not present completely whitewashed product. Times are a changing... just not fast enough.