Despite of the earnest efforts of the music and cinema industries and their anti-piracy lawsuits, shamless copycats have been the norm during history and during the shaping of virtually every culture on Earth, not the exception. It is wired in our brains: monkey sees, monkey likes, monkey do.
The whole "asking permission first to use something that doesn't belong into your culture" or wanting a "collaboration of cultures" is absolutely unrealistic. There are no representatives of a certain culture, for culture is by design something nebulous, abstract and quite antithetical to institutionalization. And like the saying says, there's no more sincere form of flattery than imitation.
Another entirely different issue are double standards ("this started being cool only when XXX people do it") and mis-attribution ("white people invented rock").
Mis-attribution is simply a matter of education and frankly, it affects almost every culture out there. There are a billion archievements and inventions that were wrongfully attributed to another person or culture than people thinks (
Brazilian Santos Dumont invented flight, not the Wright brothers,
zero numeral was an Indian, not Arab invention, etc, etc).
Double standards are indeed fucking bullshit, but they don't have anything to do with appropiation. They are a sympthom rather than the cause: Rock n' Roll only started to be successful once white people adopted it because white people had a disparate purchasing power and media exposure in the US. These are the true problems (economic inequality trought racial lines) but people likes to be fixated in the cultural aspect (aka, the sympthon rather than the illness) since waging cultural wars is something far more entertaining and politically safe than trying to address income inequality, I fear.
