To me, the jocular term "folk police" describes people who object to modernizing trad music such as Irish dance tunes by using non-traditional instruments or arrangements. For example, some say that Irish music should be played the way Michael Coleman, or Willie Clancy or whoever, played it; or that it should be preserved at the 1870s level, or similar notions.

To them, I say: "Folk music is not a pickle... it doesn't need to be preserved!"

It does need to be kept alive, though.

Cheers,
Michael