People about Cosplay...
Putting aside for the moment that the tone of the question doesn’t imply the most open of minds, cosplay is – simply – acting. Do you consider Mel Gibson, Ken Branagh, David Tennant, Cumberbatch, et. al. immature for wanting to dress up and act as Hamlet? Cosplay is a similar – if not identical – mindset: people, inspired by characters, possessing the right combination of talent, bravery and self-awareness, performing as said character for an audience. Whether it’s a convention stage or a Broadway stage makes no difference. The person who portrays Deadpool or Master Chief is very much spiritual kin to the person who plays King Lear or Hamlet. It’s wrong to praise one and denigrate the other based on the source of their inspiration, for to declare which works are “great” and which are not is subjective or worse. Still, even if most consider it blasphemy to compare Marvel to Shakespeare, the motivation to portray characters from either realm is identical and the healthy mindset WON’T criticize this, realizing that whatever it doesn’t “get” is not automatically inferior or invalid.
PS: Ironically you will find, if you but ask, that most cosplayers as children were very successful Trick or Treaters, as Halloween is quite often the “bug” that bites them for their subsequent motivation.
Ancient peoples dressed up as animals and gods. They dressed up as powerful characters of myth and reenacted stories that were important to them.
Modern people do the same. On Halloween, people dress as archetypes of many kinds, At Christmas, you see people dressed as Santa Claus in the US, reminding us to be kind to others, even if we don’t put change in this particular pot.
Once, I was in an Indian restaurant and as I waited to be seated, I looked at pictures of a party at the restaurant. They had two people cosplaying Krishna and Radha.
I attend anime/manga gatherings and I know from talking to many, many people about this, that the drive to dress up as characters you love comes from wanting to participate more deeply in the narrative.
At Renaissance Faires, I was quite often told by people “this is my real self,” as opposed to the normal worker bee they were during the week.
And then there is cosplay as a sales technique. Booth babes are hired at tech and industry shows because getting a dorky guy over to the table takes work. Geeky folks are cynical folks, but a pretty girl will draw many men without working at it. Once they are there, they must of course be engaged and thrilled by the tech, but the hook is the girl. Or in a maid cafe in Tokyo, having someone be kind to you, call you “Master” and do your bidding feels good, even if you’re paying by the hour.
So, why cosplay? To engage with our mythical/narrative roots; to take on skills and powers that we don’t normally have, in the context of ritual – or fun; as a visual hook to drive commerce; to enjoy, for a moment, the thrill of being something else than we are or who we feel that we really are.
We may not all cosplay, but we all play dress up from time to time. Next time you slip into tux or a really nice dress, think about the cosplay you’re engaging in – what are you projecting? What makes this you different than the everyday you? What powers, skills, qualities are you pretending to have?
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.