But… But… He appropriated from the Slovaks! And the Romanians! And the Bulgarians! And the Arabs in Basra! 
More seriously, Bartók was one of the very first truly professional ethnomusicologists, he was extremely good at encouraging a pride in indigenous music-making in other nationalities, and he used his materials with great individuality and sophistication. Great composers steal like magpies. By the time they have finished stealing, though, the materials have become theirs entirely.
I’ll add that I was very good at limiting the list: I could have added quite a few more musicians I’m very fond of (probably starting with Prokofiev).
Off topic a bit: Can you have a look at this (over in the crafting thread) and tell me what you think? I’ve not got a lot of feedback yet, and I’m still in the “Have I done something good, or have I perpetrated a crime?” stage of things. If there is even a whiff of the latter, please let me know where you are catching the whiff, because this is also the “Better revise!” stage.
