As you may know, Lennon loathed that McCartney tune. In fact, the placement of the track on the album, "Let it Be", was meant as an intentional slap in the face of Paul and religious people.
The track is sandwiched between 'Dig It' and 'Dirty Maggie May', the latter being a song about a whore. (NOTE: Mother Mary is actually not a reference to Catholicism. Paul's mother's name was Mary. You cannot deny the religious/spiritual feel of the tune, however. Most certainly Paul would known that people would have viewed it as having spiritual overtones.)
Lennon and Phil Spector are largely responsible for the lineup/production, and some of this directly led to the culmination of things that caused the Beatles to split.
As well as some of Lennon's snide remarks on the album. I've read where Lennon wanted Spector's infamous 'wall of sound' to ruin McCartney's songs on "Let it Be", particularly "Long and Winding Road".
I think the film is very hard to watch. Not just because it's put together badly, but because you see the band breaking up.