eric the Red:

[Colin Irwin] often repeated the erroneous fact that Ewan MacColl was born in Auchterarder, when everyone else in the world knew he was born in Salford.

"Ewan MacColl is that rare combination of traditional and revival singer at one and the same time. Born in Auchterarder, Perthshire, Scotland..." From Broadside Ballads [Folkways 3443, 1962], notes by Ewan MacColl.

As the above shows, Ewan sometimes claimed (or allowed his publicist to claim) that he was born in Auchterarder, and moved to Salford later.

So, yes, MacColl lied a bit about himself. Lloyd lied a fair bit about songs (see the Reynardine thread and the Recruited Collier thread, which both have a link to my 2004 scholarly article, for more on Lloyd's approach). I wouldn't venture a guess on Brian P's question about "four loom weaver," but I wouldn't put anything past either of them when it came to reworking a song into something they liked better.

As to the original question, Friend or Foe of the music? MacColl made huge contributions, and will be remembered for them long after our comments here are forgotten. Brian Peters continues in that tradition (as do many of us, I'm sure). So, I would say, "friend."