Crikey, I'm not claiming they ripped off the underground. I'm just saying that virtually everything they did was inspired by other ideas of the time. No doubt, whatever they took, they made their own and unmistakenly crafted it into the Beatles, fashioning their own sound out of it. And besides, of course they'd never sounded like their inspirations - The Beatles' overwhelming focus remained melody and pop, while the other banRAB were trying to do the exact opposite.
So it's not a claim against their credibility, but against those who try to assert that they invented all of their ideas organically and were therefore the great innovators of the rock era - which they were not. They were the greatest songwriters of the rock era...