A couple of years ago we were riding the metro here in Hamburg and we overheard some woke students have a conversation about sign language.
Girl: "I actually know sign language, but I always hesitate to do it in public because that would be cultural appropriation."
If this were true, if the learning of a different language were "cultural appropriation", then why learnig a different language at all? As soon as I learn a different language I risk to offend a native speaker by misprounoncing a world or lacking historical context.
Back in the day, when I was travelling the world, people would laugh at me when I made a funny mistake and I would laugh with them, when I understood why my mistake was so funny. They would ignore the mistake, if the context was clear and they would explain things to me that were important to them. So I learned that "espanol" is a national adjective, but when it comes to the language, the term "castellano" is preferred, at least by the Spaniards I know. ("Soy espanol pero hablo castellano").
To say, a person that's not deaf should not learn or use sign language in public is as absurd as saying a person that doest't have a Spanish or Latin background should not learn Spanish.
If you think this through. you are segregating the world, by claiming each person better stick to the place where he or she was born. Every cultural exchange is too risky, because somebody might be offended. Let's better have Black areas with Black schools, Black music labels, Black busses and so own. "They" can stick together within their community and need not risk beeing insulted by somebody from outside.
"We" better have areas reserved for white people only, because that's easier, too. If something happens in the "Black World" say, an athlete kneels during the national anthem to protest racism and police violence, we better stay silent. I would like to express my solidarity and sympathy for the protest, but I am not a victim of racism, so I better be silent as not to offend somebody. If I was an athlete, I would consider not to stand up for the anthem either, but this move came up in the "Black world" ("they) not in my world ("we") so it is probably cultural approriation to just take it and make it mine. So I do nothing.
Cultural appropriation is so playing into the hands of the "Identitären" which are a strong (and young) right-wing movement, originated in France but also present in Austria and Germany.