I think Greenwald is probably right regarding his accusations in the email, but I agree that they weren't necessary to include, at least so early in the discussion process. He did seem to react unnecessarily harshly, before his email even received a reply.

As you say, he was the one who first began displaying the unprofessional behavior. He probably should have just sent like half of his follow-up email (the citations of the email compared to the article) and given them a chance to reply. But I also understand why he felt he was being unduly pressured and why staying there wouldn't have been wise for him.