Hi,
Mackenzie's story can be true or false, but in any case, if I like a certain kind of music I can't stop liking it cause of a story that will never be proved to ever have existed; that "story" can be used by Mac to earn money, as has already been said, but also to free herself from a dark period she may have lived through, now that John's not alive she may not feel the pressure of his existence to tell it.
John's relatives can say whatever they think, but since John's not there to prove it was true or false, I'm not able to judge the two sides, one is missing.
In my opinion, John was, and still is, an incredibly creative artist, apart from the things that happened in his own life or the way he acted in some cases...the result of his work over the years is excellent for me, I separate the artist from his personal life.
Albert.