Cultural Appropriation

There was a news story I spotted the other day about Cultural Appropriation, which I believe is a made up term to describe something that's entirely normal. It concerned a small number of Maoris who took great exception to the NZ rugby team using the Haka. 

For a start, the NZ rugby team has a healthy number of Maoris playing for the side. Secondly, if the entire population of Nigeria (which is much larger than that of the UK) suddenly decided to start Morris dancing while wearing Dutch clogs and sporting Savile Row suits, it wouldn't worry me in the least - and why should it?

The UK is a melange of at least half a dozen cultures, each wave of invaders adding many cultural practises to what became British; Celt, Roman, Saxon, Dane, Norman, etc. Why do people get so upset about borrowing from different cultures? Imitation, surely, is the sincerest form of flattery and, in some cases, something to giggle about when done particularly badly.

Proponents of the argument maintain it's the appropriation of minority cultural practices by the majority, but how does one define a minority for a start? The Normans were a numeric minority in England after 1066, but the ruling class, and hence set the fashion. The adoption of Pacific Island tattoos by white, British males is a cultural adoption, but the Pacific Islands are nowhere near the UK.

It seems to me that it's nothing more than an invented justification for a minority to have a moan, unless someone can tell me differently.