If anything, Greenwald comes off as compromised by his own political biases. The editor says fairly gently that there are concerns with poorly-supported claims and omitting key information -- such as the media reporting on corruption claims and the fact that media outlets have not been given access to the supposed hard drive of emails. This results in a meandering and potentially misleading article that leads readers to conclusions it does not actually support.
They suggest a way to focus it more on core points which are well-substantiated and get a solid article out of it. They're not censoring his political views, if anything they're encouraging him to express them in an article indicting liberal media for going soft on Biden. They're trying to get a shorter, more tightly-focused article for publication. Which is to say, a more solid article.
That sounds like an editor doing their job -- editing is supposed to be the art of removing words, after all!
Greenwald sends first a polite reply, then a much less polite one that jumps to this vitriolic claim:
> I want to note clearly, because I think it's so important for obvious reasons, that this is the first time in fifteen years of my writing about politics that I've been censored -- i.e., told by others that I can't publish what I believe or think
Followed by insinuations that they're suppressing the story due to their political biases. It sounds like Greenwald can't accept that there may be legitimate explanations for why the content isn't focused or solid enough.
That's downright nasty and unprofessional.