The Stranger singer was referring to Elton John's comments in a 2011 Rolling Stone interview. The Blue Moves musician talked about Joel “not writing his music anymore,” asserting that it was “either fear or laziness.” Elton felt that his fellow singer was “coasting.” He further remarked on the canceled tours and Billy needing rehab:

In his new HBO documentary, Billy Joel addresses his feud with Elton John and talks about his career; however, it quietly ignores one major aspect of the musician's life.

Billy Joel opens up about DUI rumors, his friendship fallout with Elton John and his struggles with alcohol in the HBO documentary 'And So It Goes'

John’s full quote wasn’t exactly subtle. He blamed Joel’s alcoholism for tour cancellations, accused him of “coasting,” and described Joel’s rehab stints as “light,” quipping that when he went to rehab, he had to clean the floors, while Joel had TVs.

So It Goes’ will fully prepare you to teach a college class on Joel the angry young man, Ex-Wife Guy, and unlikely superstar.

Billy Joel has a right to his opinions, of course, but many might not like his stance on one legendary Beatles album.