Lighter, I think we've been here before!

Now if I said to to you Rock is a musical style, Jazz is a musical style, Classical is a musical style, would you disagree? No, of course you would not.

Folk was the word coined to describe a musical style as 'Rap' has been more recently. Now I personally have no issue with the word 'Folk' being used to describe the style of a song written 300 years ago, or yesterday!

I note MGM Lion's comments above about the trades descriptions act, well, that's pretty well every folk club and festival countrywide, perhaps you and he might like to fund the test case?