When it comes down to cultural appropriation, there are many factors that come into play. People isn't really mad that an idol is wearing a hairstyle that usually they tend to use, but rather the difference in response that provokes in general audience: black people were constantly bashed and discriminated because of those hairstyles (lets not mention that those kind of hairstyles aren't just for fashion but specially because they adapt to the genetics of black people, other races can get their hair damaged or even lose it with these styles), but when a white person (or in this case, an idol) wears them, everyone considers them "trendy" and "just a hairstyle".
I'm not black but I have listened to this thing going on. It's not about the clothing, the hairstyles or whatever, is about how y'all react when a person from that culture wears it and how y'all react when your faves are wearing it.
If we made no difference, I guess everyone would be okay with that!