Kate Rusby does indeed use the term in her stage act, as part of her banter. She jokes about (for example) turning Ranzo Ray into a "girly song".

However, I have heard established folk singers of maritime songs huffing and puffing about precisely that: Kate turning Ranzo Ray into a girly song! We also heard on the programme, and have seen in postings on this board since, claims that people shouldn't learn folk songs from CDs, and shouldn't sing a traditional song themselves until they have studied how it has been sung by a traditional singer.

The "Folk Police" is a joke: but like the best jokes, is well rooted in reality. They are visible (or audible!) to others than the naive neophyte who knows little and cares less, and deserves what he/she gets.

The songs are not harmed by being reassessed and sung in different ways - the originals are still there for those who prefer them like that. Perhaps that ought to be remembered more often.