I have no problem with somebody calling a
particular act of 'cultural appropriation' negative
if it is in fact negative and the harm can be demonstrated.
I have a
very big problem with somebody calling all acts of 'cultural appropriation' negative (which the mythicists do), and with assuming that any selected act of negative cultural appropriation is negative because it is cultural appropriation and for no other reason without demonstrating it.
And, as has been demonstrated, your explanation is based on a false premise.
No, it's not. The ordinary meaning of the term appropriation implies taking something from someone and making it one's own. But I've also, for the sake of argument, accepted the term as it is.
That's it? Somebody copied the design of a garment of a person who has been dead for over a hundred years?
The most generous possible concession one could make in this case is that it has some elements that might be considered a violation of intellectual property law, since her great-great-great grandfather presumably designed the garment and designers are afforded exclusive use of their designs for a while and that State-granted exclusive use can pass to the heirs of the designer. But that has not happened here. Somebody
simply copied a 150 year old design over which nobody has a moral claim.
And note that the cultural appropriation mythicists would
not need to rely on it being such a blatant copy to condemn it.
Any garment that was 'inspired by' or that took visual elements of an indigenous culture's design conventions and arranged them in a new way would be deemed a cultural appropriation and therefore automatically condemned.
If that's the best example you've got (and I admit it is less obviously ridiculous than cornrows and twerking), then I'm afraid I'm unconvinced. The feelings of an individual were hurt, but that does not separate this case from the more obviously ridiculous cases.