"My argument is simple enough - the Traditional Songs aren't ours to mess with"

"The most important thing any Revival Singer of Traditional Songs can do, therefore, is by way of research & sourcing, not changing the songs to suit their purposes."

Everyone who sings traditional songs changes them, to some degree or another. They aren't museum pieces, and if they were there would be no need to sing them at all - we could just go back to the recordings. You yourself take considerable liberties with melody and phrasing (if your youtube postings are representative), so why are you up there on that hobby horse telling the rest of us what to do?