I grew up around bluegrass music and that type of attitude is one of the things that turns me off about playing with many "bluegrass" musicians. I think they fail to see the music's true origins and they mistakenly believe that it is some type of new genre of music that was invented by Bill Monroe, Flatt & Scruggs, etc. The five-string banjo was really the majopr musical innovation that brought in modern bluegrass, IMHO, but the music itself was, and is, simply traditional mountain music that was passed down and evolved from our forefathers.I sat in with a Bluegrass band's practice session once.
One of the wives said, "It sounds like that Celtic crap to me!!",
What is most irritating is that many traditional "bluegrassers" are not only very pedantic about what songs can be played, they're extremely rigid about what instruments can be used. Irish musicians seem to be more open to adapting any instrument to their music- like the bouzouki, the accordion, or the 5-string banjo.