The reaction to the post is supposedly an x-risk

Yes, but not in the way you seem to be saying. I was semi-joking here, in that the post could spook people enough to increase x-risks (which wfg seems to be trying to do, albeit as blackmail rather than for its own sake). I was referring to how in the film Dogma gjb snyyra natryf, gb nibvq uryy, nggrzcg gb qrfgebl nyy ernyvgl. (rot13'd for spoilers, and in case it's too suggestive of the Basilisk)

if we let on we can be manipulated that way, then a UFAI can do extra harm.

It can? I suppose I just don't get decision theory. The non-basilisk part of that post left me pretty much baffled.