"You are imposing a formality on the nature of folk music which is utterly counter productive - and really is based on some desire to give it middle class respectability and status."
No!... this is completely arse backwards.
No-one's imposing anything on folk music. It's the other way around. People hear that folk music strikes the ear in a distinctive way and analyse it in a bid to understand what gives it that character.
What you find is that there is a loose set of traits that is characteristic of a folk tradition. No one song within that tradition will have all of those traits. Some might have very few. It's a set with fuzzy boundaries. But it's still a real set and it maps onto our immediate reaction to hearing folk songs.
The music of Oasis doesn't trigger the same experience, because it doesn't have those same characteristics.