"...take a pair of scissors, some Scotch tape and a book of traditional Scottish songs and you can 'compose' Mull of Kintyre"

I'd doubt if that's actually true - but if it was, what's wrong with that? Some idea that if music and songs aren't off-this-planet original they are useless, and that for a new song to grow out of old songs means it's worth nothing?

I'd be inclined to say that that kind of thinking isn't what folk music is about. Or indeed, music in general.

.....

As for the Frog Song:

"Win or lose, sink or swim,
One thing is certain we'll never give in,
Side by side, hand in hand, we all stand together..."

Nothing wrong with that. It's not high art or portentious, but it's true, thank God.