here is my guess:
Damoclean means "threat of destruction"
There are three different Urijah's in the Bible, all doing different things.
Here is a
LINK to basic descriptions of the three.
If I were to hazard a guess, I would say it applies to the third Urijah.
I base my conclusion on the use of the word "Damoclean" and the fate of the third Urijah. I am left with the impression that this guy thinks that great bodilly harm will come to him if he should speak more openly.
Edit: yeah, I am pretty sure this guy is likening himself to the third Urijah and is trying to infer that a similar fate would befall him for "speaking against the king", with the king being GWB.