You might want to look at the video again. Pollack wouldn't have been close to hitting the throat or jaw. And launching is a bit of stretch. Now if it was worth it for Pollack to deliver the head butt or not is hard to say. Maybe he felt that Pollack would have put a helmet on the ball. Or probably the likely result is that he just reacted in the .1th of second and what happened happened.
I saw the replays, and Pollard launched leading with the crown of his helmet. Ridley ducked his head as a defensive instinct, otherwise he probably would have been hit in the jaw or throat by the top of Pollard's helmet. I have seen flags and fines for much more dubious h-h contact.