I don't know how to put this more plainly. This is not a thread about what is and is not folk. I am happy to debate whether Macca is musically important or not as that is pertinent to the thread but what should and should not be sung at folk clubs is being done to death next door (currently) on the Folk revival thread.

To bring us back to the point there is a swaithe of people who list the Beatles, including McCartney as an influence. Whatever you say, that makes him musically important. Without him a lot of artists and bands would not be doing what they are doing today. In addition, Yesterday is still the most covered song ever. Pretty important I reckon.