I can actually see why most people would not understand the link between the song and Jagger... I have listened to it countless times the past several days, trying to make the relation between the two, and I would have sworn up and down, if not for the interview, that it would have been about Brian, or another friend from long ago... like a friendship he had sacrificed for something else... but it's kind of hard to argue with the reasoning when the actual writer tells you what it's about.
But, regardless of what Scott says about the song, people will ALWAYS think that the song is about what they get from it... using, as an example, Tim believing that it is about Christ.  Regardless of what anyone tells him, if he believes in his heart that it is about Jesus Christ, then nothing will convince him of otherwise, as it's a feeling that he has deep in his heart.