"It's a strange sort of cultural relativism which says that only the original communities have the right to decide what happens to these songs"

It would be if that was being suggested. What is important to point out is songs were dying because their original thrall no longer held sway, either because fashions had changed or they were supplanted by different media. I don't see 'anger and despair' being the appropriate driver of preservation any more than we can despair that green diesels don't pull coal wagons or housewives in turbans don't red-lead their front door steps each morning. Indeed the conversation would barely be worth having if 'anger and despair' weren't continually wheeled out as an objection to anyone who tried to displace a wholly sentimental view of such changes with an objective one.

Emotion will and should play a role in the life of any well-rounded individual, but firing broadsides at anyone who questions the rationale behind preservation, or the assumptions about the way such preserved artifacts are re-cycled is letting their spleen shout down their brain.