Tom, this is from Greg's most recent blog post. It is very relevant to his views on the subject of this thread.

4. Here's a big one. At dinner I argued with Jim and Tony that if we agree that our only authority to speak to governements or to anyone else is the moral authority we earn by sacrificially serving others, and if we agree (as we do) that the Church isn't remotely close to having this moral authority in western culture, then, I said, doesn't it make sense for us to BE QUIET about politics and put all our energies into motivating and mobilizing the church to be the Jesus-looking kingdom we're called to be in order to perhaps someday gain this authority? And if the Church ever did win this broad respect such that people and government actually cared about our opinions, then we wouldn't have to demand it. It would come naturally. (Moral authority, I believe, can NEVER be demanded. It must be earned).