I've probably written those words or similar myself, Folknacious, and they do exist even if, as Ian Mather suggests, they could usefully bugger off.

I first encountered them at a folk club where floor singers knew guitars and material not seen as traditional were frowned upon (I remember at least singers who took delight in defying them just to wind them up). Then you had the Irish purists for whom it was unacceptable, depending on the strain of purism, for 1) anything to be accompanied 2) anything to be accompanied except on specified, vetted instruments or 3) tunes to be played by combos instead of on single instrument.

It's all bollocks, of course, though I would not try to stop none running a club or performing music in a way that conformed to their narrow outlooks. No one is forced to attend/listen. Mind, I'd go to a pub not selling real ale only if its wine by the glass was drinkable.