IMHO you can't appropriate a culture that's been put up for sale.
When a culture has been canned, commercialized and exported for sale abroad for decades, there's nothing to appropriate.
I think the criticism of appropriation is somewhat valid if you start taking some third world culture's folk music and then record it with white artists and try to copyright it and make millions off of it and never pay a cent to the original artists. But Japan and Bollywood for another example, they've marketed their cultures and I think the whole appropriation criticism is bull.
I think Whedon has "appropriated" feminism and used a cheap version of it to offset his fetishes and soft core porn fantasies he keeps writing into his stories.