While I agree on principle, it is to be noted that one was fanart and the other is an actual actress role. Which actually means the latter is more of a substantial change than even the most loud of Nessa whitewashed fanarts there were.

I got you:
Blue-haired being:
Respect the character!
No to the change of race!
Whitewashing is racism!
Mildly upset looking fella:
Respect the character!
No to the change of race!
Blackwashing is racism!
Blue-haired being:
Blackwashing does not exist, it is not racism, it is diversity! What affects you the color change of a fictional character? Everyone can have their vision of a character, you are racist!

or something like that