Mel Gibson is telling friends ... he NEVER said John Lennon deserved to die -- in fact, he's a huge Beatles fan and he plays their music all the time.
Sources tell TMZ, screenwriter Joe Eszterhas' allegations the actor celebrated John Lennon's death are just false. As one source put it, "It's not uncommon to hear The Beatles at Gibson's house."
The source adds, Gibson was even playing "Imagine" at a recent function -- the same song Eszterhas says Mel bashed recently, claiming, "Imagine. I hate that f**king song. I'm glad [Lennon's] dead."
Mel is claiming ... he isn't surprised by Eszterhas' false claims in his 9-page diatribe -- because the entire letter reads like a "bad script."
We're told Mel is also convinced ... another major rift between him and Eszterhas had nothing to do with him -- or "The Maccabees" -- it had to do with Mel's other viking-themed film project, which Mel's been developing for years.
We're told Eszterhas was frustrated with Mel ... because Mel had been putting more time into the viking movie than he did into "Maccabees."