I have to admit I haven't listened to very much Ewan MacColl, but on the subject of adopted accents in general, I don't really see what the fuss is about. If he did, he was hardly alone, even among respected musicians who undeniably contributed a lot to folk music in general.

I've sort of got opinions on both sides of this--on the one hand, I hate a phony accent if it's not really needed. I saw the Old Crow Medicine Show last year and was sorely tempted to tell Ketch Secor that he needed to stop the fake Southern drawl because it was both embarrassing to himself and verging on insulting to his audience. I didn't like it about the New Lost City Ramblers, either. Just me.

On the other hand, sometimes a song doesn't come out right without its "native" accent. An old song in a Scottish dialect sounds really weird sung in an East Texas twang (I've heard it. It ain't pretty), even if that is what is most honest of the singer. Unless we want to translate everything into our own form of English, which would spoil the beauty of a lot of good songs, my personal feeling is that we can cut people a little slack on borrowed accents.