Jerry Westerby wrote me in response to my Safire query:

I can’t remember (and a cursory search of my files was fruitless) who first speculated this but the hypothesis goes that Safire is furious at Karl Rove et.al. for using him and his column to disseminate the “we had solid information that the White House was going to be attacked” lie that was used to justify W being sent to an underground bunker on 9-11. If you remember the lie, the person who called in the threat had knowledge of some kind of inter office codes that made the threat creditable. Safire then speculated in print that there must be a terrorist mole in the White House. Rove confirmed the story to Safire. When the story was exposed as a huge lie, Safire was apparently irate, not only at being lied to, but also for being used like some common reporter for disinfo, being made to look the fool for the mole nonsense, and being left out in the cold by his friends as if he had made it all up himself. This story is plausible, but then again Safire has always had a discernible if slight libertarian streak in him, so maybe his criticisms of the administration are nothing but sincere horror.