People about Cosplay...
Absolutely! Just not in the way your potentially-leading question could be interpreted to imply.
Wikipedia says that “cosplay” broadly applies to any costumed role-playing in venues apart from the stage. Therefore, it’s only the growing and disturbing layman’s trend of equating “cosplay” with “manga/Japanese” which makes it appear there’s a problem. My generation was cosplaying before the term was coined (c.1984), and thus we “costumed” at conventions as characters from Star Trek, Star Wars, Ghostbusters, Doctor Who, Marvel and DC comics, etc., none of which are anime or in any other way Japanese in culture. Even if some were, most other characters equally originated from different countries and cultures, so on the surface the answer would appear to be “no”.
Now, is cosplay appropriation of any kind? It’s actually nothing but! By definition, cosplay is of a previously-established character from a previously-established distributed media venue (TV, film, books, etc.). You’re always cosplaying a character which someone else invented, or at least basing in on one (crossplayers, etc.). You’re not asking the creator of said character to do so, so yes, you’re appropriating it. But it’s an appropriation of trademark or license issues, not of culture… all cultures are potentially fair game for it.
Finally, cosplay itself has matured and spread enough that Wikipedia already classifies it as a “subculture”, which I suspect is a conservative definition if you’ve ever been to a comic-con.
So: cosplay is, in the end, a “culture” based on “appropriation”. If we concede that this encompasses any culture and appropriation, then your answer is a resounding and unabashed “yes”.
Cosplay is used to portray a character, in complete characterization, sometimes even down to speech and acting.
Culture appropriation, in my opinion, is always negative, portraying double standards that favor white people. For example, hairstyles used by black people seem trashy and inappropriate, but in white people they are deemed edgy.
Cosplay is a representation of the love for a character, they are acting as the character, their race or cultural background of said character usually has nothing to do with the character, it is a simple fact about them.
When a person does “cosplay”, by making fun of another race, say they dress up as a black character by simply putting on brown makeup, this is racism.
However, correctly portraying the character who happens to be black, is cosplay and is not appropriating the culture of said character, simply using their image to act as them.
When judging whether something is cultural appropriation, ask first: is there a cultural double standard that praises the borrower while punishing those whose behaviors/styles are being borrowed from? If not, then the second test is to see if the thing being borrowed has religious/spiritual/historical significance the borrowers are disregarding or disrespecting for the sake of ‘cool’. Finally, does the act of borrowing reinforce stereotypes?
To answer your question, No. Cosplaying in the past hasn’t been used to marginalize, dehumanize, or stereotype the Japanese people. Cosplay has no major religious, political, or spiritual significance, even in Japan it is considered a commercial hobby. Cultural Appropriation is problematic because the hegemonic group (in the US case, white people) get praise for behaviors the group that they borrowed the practice from get penalized for (in this case, Japanese otaku). However, Japanese otaku have the same or superior status as American Cosplayers at US Conventions and English language internet. Japanese Otaku are not facing a double standard when compared to white otaku that favors White otaku.
There are some racists who may say white cosplayers look more like the anime/video game characters then Japanese cosplayer, but those types tend to be seen as racists and pariahs in most well-balanced cosplay communities. Most people tend to think the Japanese have very high quality cosplay.