I suspect the part was sung by "Faul" the fake Paul McCartney, who took over the real Paul's role after the real Paul died in that car accident ("He blew his mind out in a car"). Don't try to feed me any of that Guiness heir stuff. We all know EMI (Electric and Musical Industries) is just a front for British Intelligence and that they tried to take over the world with their Tesla death rays and the Beatles.
I mean, it's obvious, dude! They were pushing all this peace and love so that when we were unarmed Uncle Joe and MI5 could become our overlords. The long hair would make the men more effeminate and also mess with their aim. The LSD--everybody knows that was an army experiment--Uncle Joe and Co. needed a way to get drug use to the masses (a literal "opiate of the masses" since religion was wearing thin).
John recognized his role in the conspiracy (and tried to put out secret messages--I buried Paul, the Walrus was Paul, etc.), but was given a "minder" when he became too active.