Yeh but you know, she darkened her skin = blackface.
Thats the thing though, she didn't. She is wearing a full body suit to transform her appearance completely. Which by any rational standard is a completely different thing, as the racial aspect is just one component of many things being cosplayed.
If people are "outraged" and "offended" having seen the lengths taken in creating this characterization, they are being blatantly dishonest. If not, and are reacting based on hearsay then that's just foolishness.
The point is this, and its real simple. There HAS to be a real, arguable, reason as to why something is offensive, otherwise its just unthinking prejudice.
I can get why white people should be discouraged from using the term "n*gger", even if its not used as a slur or with any harmful intent, the history of its use by whites against blacks gives it a sort of latent power. The idea of the black community reclaiming the word for their own use is empowerment, and I'm totally down with that (as if my self censorship in this example didnt give the game away!)
Blackface is not the same, because having dark skin is not a slur. Its not a BAD thing, it just a trait of people who's genetic heritage belongs to certain geographical regions. Hell, the concept of "blackness" is a relatively recent invention, and that's kind of the crux of the matter.
Without the crucial connective logic of "blackface" as a 19th century theatrical tradition and its connection to reconstruction era American history, and the "Jim Crow" laws left in its wake, what's left is a belief that changing the complexion of one's skin is a moral sin in itself. In a strange inversion of the pattern of historical prejudice, "whiteness". having white skin is like the mark of cain, its a marker of shame that cannot be covered.
Its a weird, essentialist viewpoint that is utterly divisive. Its bizarrely antithetical to the idea of unity and togetherness of all human beings and is the absolute opposite of what I'd consider to fall under the umbrella of liberal or progressive politics.
Sorry, long post, but to sum up it seems to me that to be inflamed over this you need to have literally forgotten, or be oblivious to, the reasons why its supposed to be bad. Its mindless, reactionary and above all else performative. It's basically acting based on the logic that "its just the way it is"... and yeah I;m thinking of that God awful (but curiously apposite in this circumstance) Bruce Hornsby song as I'm writing this!