Given that since he was shot, the keepers of John Lennon's flame have been quite happy to use his name and music to flog everything from regional airports to training shoes - to say nothing of John Lennon's Flame brand barbecue coals - it's something of a surprise to discover that people still get upset by it.
But they do, and so we find ourselves with Sean Lennon having to defend why Lady GaGa was allowed to use Lennon's white piano.
You know the white piano - it was the one in the video where John banged on about how we'd all be much happier if we could free ourselves from being fixated on physical stuff; from treating things as if they were somehow of intrinsic value themselves and to concentrate instead on the spiritual.
Apparently that message of not treating stuff like it was a god has had such a deep impact on Lennon's fans, they can't stand to see people putting their hands on the piano Lennon used to float the idea. Hey, you, get your hands off John's stuff:
JOHN LENNON's son SEAN has been blasted by fans of the late BEATLES star for allowing LADY GAGA to play the musician's iconic piano.
Yeah - how dare Lady GaGa, a mere pop star, put herself on the piano keyboards of the bloke who did Twist And Shout and I Wanna Hold Your Hand. That's just wrong.
Sean defended his decision to allow the pop sensation to use the piano - insisting his followers shouldn't be "so judgemental".
In a series of posts on the microblogging site, he writes: "Pianos are meant to be played. Why is everyone so uptight?
"What should we do, lock it away in a dusty room? So judgemental... Come on, lighten up... life's too short, there're enough real problems in the world.
"Firstly, he gave that piano to my mother for her birthday, it is hers, secondly, he was not uptight the way you seem to be."
Of course, if Sean really wanted the piano to be played, he could give it to a school that wants to teach kids to play piano but don't have the money to buy one. Eh, Sean?