It was precisely that.
By all accounts he was given feedback on his ideas before the final memo went out.
By his own account.
In the very text he says that opposition to these ideas demonstrates bias and he therefore dismisses the very idea of being wrong.
Quote, please.
This wasn't some intellectual debate.
No, the reaction to the memo turned out to be screeching and namecalling.
Here's a feminist interviewing James Damore: https://www.youtube.com/watch?v=5SFLoKa8FdA