To make it clearer what I don't mean, here are some cases in which I think cultural (mis)appropriation might be a legitimate accusation, examples of some things that ought not to be done:
1) Someone makes a ton of money off the culture of a historically disadvantaged group, and doesn't share any of that money. This is an accusation Kevin Costner faced after Dances with Wolves. After the movie, in which Wind in His Hair is super grateful to John Dunbar for being a white man who really understands the Lakota (to no avail), Costner then opened a multi-million dollar casino in Lakota territory, irritated the Lakota by trying to trade for land they considered theirs, and then never actually built the casino. A lot of Lakota were understandably angry. Dude made a lot of money acting like some white savior of Indians, then didn't really do much for any actual, living Indians, although the Lakota reservations are in pretty grim conditions.
2) Rather than borrowing from another culture, a member of one culture tries to flat out act like a member of another culture. I'm out of my depth here, but Iggy Azalea comes to mind. Or pretty much all K-Pop that mimics American hip-hop. Exhibit A. Annnd, exhibit B:
The thing about this second argument, though, is that it's more of an aesthetic argument than a moral argument. Since the line between appropriation and inspiration is hard to delineate, it's probably better not to approach it prescriptively. This video sucks not because it's immoral, but because it's a cheap imitation of something already done elsewhere, and it doesn't really add anything of its own. But that doesn't mean no Korean should ever lay down some R&B beats.
So what's bullshit, then?
I write a lot of stories about other cultures. I'm a translator, and I spend a lot of time observing people with obvious ethnic and socioeconomic differences from me. So when I daydream and then suddenly realize I've just been dreaming about a story, it's often not about people like me--bitter white dudes trying to delay suicide until their parents have died and their kids are grown up. In my upcoming book of short stories, four are from the point-of-view of Africans. Two-and-a-half are from the point-of-view of a woman. One is partly from the POV of an African-American student in Baltimore.
What's bullshit is that someone might claim this represents theft. For one thing, theft isn't anything new in art. "Good poets borrow, great poets steal" is one of those long-repeated phrases in art (attributed often to T.S. Eliot, but he didn't really say it). There is even a writer advice website dedicated to how writers can best steal ideas. Every writing how-to book discusses stealing.
There are, of course, ethics to stealing. We don't plagiarize. The idea is to find something someone else did, tear it apart, and then make it into something different, better, or more interesting. Sort of like Chinese techno-piracy only it's okay because nobody really makes money off of books anyway so you're not really infringing on valuable intellectual property.
If I used the pen name Tewodros Gebre-Igziabhier and pretended I really was a Habesha writer to get my Ethiopian/Eritrean stories published, that would be cultural appropriation. (If you don't know, one white poet made it into the Best American Poetry anthology a few years ago by pretending to be Chinese. A cheap trick, yes, but one that pretty much revealed, if anyone was in doubt, that nobody has any idea what makes a poem "best" these days. The editor of that volume? Sherman Alexie, who has written stories with characters who viscerally hate Jim Morrison for ripping off Native American symbols in his music.)
I don't pretend I'm Ethiopian. I say I am what I am--a white guy who has watched a culture from the outside, and here's what I've seen. If it's interesting, read it. I found it interesting. I don't think that's misappropriation. It's normal writing.
Like any gift given to us by theory from the academy in the last 40 years, there is probably some valid underpinning to the idea of cultural appropriation straining to get through all the bullshit. But students seem to embrace theoretical concepts without really grasping what they've read. I know that was true when I was in grad school. Without the ability to understand the theory with any subtlety, all its proponents can do is grasp onto a few key phrases and use them to beat their opponents to death with. They will assert that for a white writer to write a minority protagonist--or, in some cases to write minority characters at all--is cultural colonialism.
I realize that my reading of Ethiopians or Eritreans is filtered through my own, privileged, white, male, Western perspective. (That's pretty much everything you'll get out of reading Edward Said's terribly long Orientalism--I just saved you a ton of time.) That doesn't mean it's an invalid, immoral, or unworthy perspective.