"We need the purists to keep the different genres distinct" - that can in a way be true. Though I prefer it when you have musicians who effortlessly and with good will switch between say Irish and old-timey or whatever or take a break if it's something they don't feel they can play (like in the session I was in last night).

But the real problem GospelPicker hones in on here isn't so much purism, it's cliquey competitivness, which is something different.

A purist might have strict views about which instruments belong together in an ensemble, and what their roles might be, buty a purist with musical taste would also know that there's no merit in playing things faster than feels right. And that playing slow and still getting it right is a lot harder.

And as has been said, it's not just in bluegrass you get this kind of thing.