"That line that describes her skin to hold the qualities of a rose leaf."
Qualities, yes, but not color. Again, please provide a source clarifying that HCA did indeed intend for her to be green.
""Is it ok for whites to play humanoid mythical creatures from non-white cultures?"
Sure."
But if that were done, people of color would be upset about it, and rightfully so. So it shouldn't be done to European humanoid mythical creatures either.
"Well obviously as a Human, she should be white. It would only make sense. As a mermaid it doesn't really matter"
Ariel transforming from black to white in addition to transforming from mermaid to human would look like the movie is overtly trying to imply that being black isn't pretty enough to get the prince to like her. I'm not remotely attracted to black girls, but that would be a REALLY BAD message to give to young black girls. Ariel should be white as both a mermaid and a human, as she has been iconically depicted by Disney for 30 years, and has been depicted in every pre-Disney adaptation/illustration.
"I thaught its our job to call you guys Racist when running out of arguments? I was thinking that such a studio would fail, not becauae its black, but because Disney would buy it out, if it lools profitable, juat lile they've done with Star Wars and what not. Do show me where I explicitly said they would fail because they are black. I hope you know that this attempt of yours is a strawman?"
Your argument is implying that white-founded/owned studios making movies for blacks is just something they HAVE to do. It's essentially a form of the White Man's Burden. Disney has given a great deal of representation to black people over the decades, even though it ultimately owes them nothing. If black people so greatly desire to have their stories told, then they need to be more ambitious and proactive about doing so. You're creating an excuse for them not to try, and work hard.