The Western culture of personal autonomy and equal dignity is a precious thing precisely because it is not universal. Those who participate in that culture and enjoy its benefits may hope—do hope—that it may someday become universal. They may hope that their culture will shape the shared future of all humanity. But it is not a universal inheritance, and it is not the universal contemporary practice. If anything, that culture is at present in retreat, challenged and assailed both at home and abroad. It needs defending, and to be defended effectively it is vital to understand precisely how non-universal it is.
To the extent that the cultural-appropriation police are urging their targets to respect others who are different, they are saying something that everyone needs to hear. But beyond that, they can plunge into doomed tangles. American popular culture is a mishmash of influences: British Isles, Eastern European, West African, and who knows what else. Cole Porter committed no wrong by borrowing from Jewish music; Elvis Presley enriched the world when he fused country-and-western with rhythm-and-blues.