So, outing the guy will likely silence him.
I would say that's a rather serious point in the freedom of speech issue at hand. Does causing an influential blogger to stop blogging serve the public good? Weren't his readers expected to make up their own minds anyway?
If the blogger outed himself had a hidden agenda, using his anonymity or pseudonymity to wilfully misrepresent himself, I might agree outing to be justified. Now? It's an infringment on his rights. That is, if this is indeed a case where he's venting private opinion that he otehrwise couldn't because he's a public servant by day. Which in my book is an enabler, not an abuse.
Of course, some people choose to abuse their anonymity. But knowing that is no reason to ban anonymity. Or should we ban all people just because some are very bad people indeed?