Doesn't it all kinda hinge on how peeps interpret NG's use of the term 'proper folk song'?

We don't really know what he meant by that - whether it be a traditional song, or a more modern composition that's been adopted by folkies?

If the latter, then any composed song with a known author that's been adopted by folkies would fit. If the former, then he doesn't know what he's talking about.

Either way, it is pretty shit that a supposed scholar would make up something, pretend to have 'discovered' it and then pass it off as the real thing. That's shitty charlatanism in any field.

As for Bragg's parody, it works well in the context IMO - so long as the violent bits are left out. I can't see any objection to a parody of a song that was fraud in the first place!