I'm like, wow, talk about biting the hand that fed you and your family. I thought the story was that the Halls were in a financial bind and on the verge of moving back to Sam's hometown so he could take over his father's business, and Grayson getting the "Julia" role at the last minute "saved" them from that. Not that they wouldn't have adjusted somehow, I'm sure, but it probably wouldn't have been a comfortable fit all around.
Thanks to both parties eventually being employed by Dan Curtis, the Halls were able to stay in the NYC area and do a lot of what they really wanted to do, unhampered by small-town strictures. If Sam's still resentful because nobody saw him as a second Arthur Miller or whatever, and he had to work on TV dramas and such, well, he was still writing. And still is and unto whenever he passes away--- how many of us can say we not only got to make a living doing what we really want to do, using our talents (whatever they may be), and almost literally right up until the day we die?
And how many mere soap opera writers have had their work live on for decades? At some point, one just has to make peace with one's legacy, even if it wasn't one's original intention.
As for his commentary about other persons of his acquaintance, living and dead, it's already been said and much better by others here.