He also published the emails on his website here:
https://greenwald.substack.com/p/emails-with-intercept-editors-showing
I want Biden to win and maybe I am blinded by this, but it really seems like Greenwald was almost looking for an excuse to resign. There is clear escalation in the tone of Greenwald's initial reply and it almost feels like he is writing the email as a manifesto that he fully intends to publish.
He also posted his proposed article here:
https://greenwald.substack.com/p/article-on-joe-and-hunter-biden-censored
By publishing the emails and the article, I think I better understand the editor's point and there are some issues with the article. Specifically, Greenwald seems to be claiming his thesis is about media suppression when it is really just an attempt to attack Biden. For example, Greenwald says any verification is easy when it seems like sources have been less then forthcoming with their information as media outlets have not been provided access to the hard drives. Greenwald is also raising concerns over Biden's involvement in getting Shokin fired (even though he kind of tries to downplay the obvious justification for firing Shokin) and it might strengthen his argument that the media has not asked enough questions of Biden. But he goes further in heavily implying that Biden acted to purposefully benefit both his son and Burisma rather than just stating that serious questions need to be asked. He basically argues that even if Biden wasn't aware that his actions or name benefitted his son he is still guilty rather than simply arguing that the situation raises serious questions.
The editor's initial email is basically saying that parts of Greenwald's article are justified (ie, media suppression of the Hunter Biden story) but that the accusations against Joe Biden, especially with Ukraine, are pretty baseless.
It is also pretty funny, though I don't want to partake in a whataboutism, that after resigning he quickly went on Tucker Carlson to complain about media support for and bias towards a particular candidate