Well, I'd in many cases be tempted to call people doing some things "pretentious", but that's different. It's a criticism widely found in rock as well. I would not criticise (as I have seen) a singer of Indian folk songs who used her I-phone to generate the rather typical drones - it's not a pretension merely a sensible convenience (although a bit quiet beside the traditional drums).

And there are differences between people who have changed words (or tunes or timings) and those who have erred - classic examples being mondegreens which are mistakes (and will get perpetuated if not corrected).

But I really don't think I have seen or heard much of people saying things are "Wrong". I knew one woman who used to tell people how to play the timing of rigs and jeels, but since a stopped clock was in time more often than she people just used to laugh at her. She also used to say that a certain Irish tune was "supposed" to be played in such and such a key, but again people ignored her - not least because she frequently confused the starting note of a melody for its key and did not understand the difference between the start note of a mode and the key of a mode. But she is I think the only person I have ever heard repeatedly tell people they were "wrong".

Ironically there is a right and wrong in much contemporary music, because we still have the original versions and the most popular interpretations to guide us.

However the difference between folk music or song is not one of style, and is not subjective. The best working definition we have is the 1954 definition, and it fits with other concepts of folk arts and folklore so I must disagree with those who say that the concept of "folk music" is a romantic construct. It seems to be well understood in many non-English cultures (including for this purpose Irish Scottish and Welsh as "non-English) so I fail to see why it arouses such hostility in England and the USA.

But having said that, the statement "That is not folk" (whether right or wrong) is not a statement about quality, and it seems to me that it is horse definitioners who take it as such.

I stand where I did. I have not seen a prevalence of this "purism".   I don't like Americana and country and so on, but that is a different question. I don't much like most Irish music either now although once I much admired the Chieftains and saw them several times in big venues, but it's nothing to do with "purism". It's to do with what I do and don't like.

Reverting to Mr Fluids - sorry, but Jim is long since a part (and a pretty expert part but the expertise is not the point) of the Irish folk thing - you ain't (AFAIK). That makes his usage of "our" correct. And the only view I've ever heard about Rainsong carbon fibre (or graphite) guitars, or the top line Ovations with whatever backs and carbon fibre fronts is envy and lust! Yes, I have heard "It's lovely but I'd rather play a guitar" - but that's just a defence mechanism, little different from banjo or bodhran jokes.

It still seems to me that the threat of purism is if not wholly imagined at least seriously exaggerated. If the concept is absolute it has not yet been defined. By the definitions cited the question is what is "excessive" - and we are going round and round the question without getting any closer to an answer, although some who apparently dislike the concept of folk music are doing, it seems, their level best the generate heat rather than light.