Yeah, after reading their email exchange, I'm inclined to agree with the following statement from his former boss:
I agree with some of the things Greenwald says in his piece, but at the end of the day, it's Greenwald. He is, at his core, a self-serving, dishonest, bad actor. He should never be treated as a martyr based on his own account of events, because his version of events is likely to be a carefully crafted mix of truths, half-truths and hyperboles carefully and expertly crafted to benefit him.
Treat him with skepticism. Matt Taibbi, he ain't. EDIT: And yes, I'm aware they're allies in this and wouldn't be surprised if they ended up working alongside each other.