"Folkies have questioned (seriously) my use of Indian Harmoniums, Black Sea Fiddles, Welsh Crwths, North African Frame Drums, Vietnamese Jew's Harps, Hungarian Citeras and Electronic Shruti Boxes to accompany venerable E. Trads as being somehow non-traditional"

None of the above collection of exotica is any less authentic than the guitar as an accompaniment to traditional English song, of course. Even the concertina and melodeon have the slenderest of claims to authenticity in this context. What you are encountering there is simply the widespread suspicion of the unfamiliar.

"Thus Folk Music might be just as well defined as easy listening MOR pop music strummed out on acoustic guitars by an ever ageing baby-boomer demographic who've been singing the same-old same-old since the fifties & sixties."

Wasn't it precisely to escape that kind of stuff that some folk venues started billing themselves as 'traditional folk'? Thus opening themselves up to the usual accusations of purism and Folk Policing?

I see a lot of folk venues - clubs, festivals etc. - on my travels, and, although I can remember some gruesome examples of that stereotype, it's not very common. I gravitated towards the folk scene because (at its best) it was the opposite of MOR.