Oh crap - is no-one going to argue on this thread? ;-)
For which let us be profoundly thankful. Will raises an interesting point - though I'd suggest that maybe his jazz days were spent among the very laid-back or the terminally nice if he managed to escaped some of the schisms and shibboleths that get banged around. Though, as he says, nowhere near as much as folk. We do seem to like a scrap!

At the risk of being contentious, I think one reason may be that "folk" attracts the musical trainspotter - the sort of person who will never be a professional musician, but who sees folk as a medium in which anyone can make their mark and which they wish to make all their own. As such, there is a sense of "ownership" and, because such people can often be a mite insecure, a sense of panic when that "ownership" is threatened by nasty people saying that, folk or not, if it's going to be performed in public it should be performed as well as it can be, and that there's no such thing as 'good enough for folk' and that, sadly, there are some people who really should stick to the shower cubicle, the open field and the audience seats.
The big-endian/little-endian discord tends also to be a peculiarly English phenomenon. I don't see it in Wales, and I'm not aware of it in Ireland or the USA.

And Jim, thanks for a superb post; if that were a manifesto, I'd be proud to put my name to it.