Actually, I am shocked. Why'd the lawyer use Facebook for privileged communication? Why does the NSA care about someone who posted a threatening video in Norway? Hint: they don't. If they looked, it's probably because Norwegian Intelligence asked them to.( Which might well be a huge legal problem, for Norway)
In fact, it seems there is little evidence that any of this happened. Marking messages as spam does not seem like something the NSA would do and as to denying him entry into the US: if US gov is in the habit of denying visa's to those who represent a foreign terror suspect, they didn't need Facebook to establish that.
*Note, attorney client privilege doesn't apply to cases completely out of US jurisdiction with lawyers who are not lawyers in the US