"All I said is that I have yet to hear a performance by Ewan MacColl that wasn't either 1) heavily americanized to an inappropriate degree (e.g., sounds like american pop) or 2) in a ridiculously thick-to-the-point-of-minstrelsy-accent*."

Are we talking about the same Ewan MacColl here? Personally, I don't recognise this description at all. For the record, his speaking voice was sort of 'posh Lancashire' (I was going to say 'educated Lancashire' - but that would be offensive to my Lancastrian friends who all speak in an educated way, no matter how broad their accents!). I suppose that this voice was a result of his training as an actor. He also had a 'BBC voice' which was a slightly posher version of his normal speaking voice (listen to the 'Song Carriers' recordings, that he did for the BBC, if you can find them).
As for his Scottish accent, we have to remember that both of his parents were Scots and some of their ways of speaking must have rubbed off on him. Actually, my experience of him singing such ballads as 'Sir Patrick Spens', 'Clerk Colvill' and 'The Swan Swims Sae Bonny', albeit in 'thick, archaic Scots', I count as some of the truly great artistic experiences of my life (I can feel the hairs standing up on my neck, now, as I write this). I believe that these ballads only really work in the original Scots and although there have been some creditable attempts to anglicise them, some of the poetry of the Scottish versions is lost. I really do believe that, if he was to do them justice, Ewan had to attempt to sing those ballads in a Scottish accent. Personally, I think he did a credible job - but then I'm not Scottish.

Finally, 'JeremyC', I realise that some of my remarks above were churlish and intemperate and I apologise - of course you are entitled to your opinion and your own tastes! It's just that, although I'm not normally given to hero worship, Ewan had a huge formative influence on me. It's difficult to describe the impact his singing had on me when I first heard it. These days, though, all we seem to get is a sort of petty and mean-minded chipping away at his reputation and my objectivity tends to go out of the window! As Jim Carrol has often said we need to forget all of this silly sniping and concentrate on his formidable and impressive achievements.