Jesus Should Care About Caesar
Schwyzer's argument is not the usual liberal separation of church and state argument that bars people from making public policy based on "private" reasons (i.e. reasons that can't be used to persuade others because they're based on special revelations, unprovable assertions, personal faith, etc.). And it's more than just a call to be humble in one's inferences about who Jesus would want you to vote for, and to avoid misusing claims of divine authority to support political positions. Schwyzer is arguing that Christianity has nothing to say about public policy.
It's difficult for me to talk about what Christianity really is or should be. "Christianity" is a diverse set of interpretations of a set of texts and traditions whose creators were not even in agreement with each other. But I think Schwyzer is right to point out that there is a strong theme of apoliticism in Christianity. This theme is too easily overlooked by people wanting to make "prophetic" calls for social justice. It's connected to the individualistic and otherworldly aspects of the religion. One of the messages of Christianity is to keep your head down, make sure you're personally free of wrongdoing, and wait for the deus ex machina.
The apolitical streak is not all bad. It's a useful counterbalance to the temptation to hubristic social engineering. It was historically important in opening the door to the transition from theocracy to liberalism. And it can serve as a brake on attempts to misuse religion in the political sphere. Nevertheless, an apolitical outlook is at root a false one. If Jesus really doesn't care who Caesar is, then so much the worse for Jesus.
Certainly perfect justice is unlikely to result from any human government. But that doesn't mean that how human governments are organized, and who holds the various offices within them, doesn't greatly affect the level of injustice in the world. What kind of deity would be indifferent between the state of Iraq today and the state it would have been in had we not invaded? Or does he just weirdly compartmentalize our actions, so that he can't see the connection between voting for George Bush and the violence in Iraq? Does Jesus really not see that there is a great deal of suffering in our world that is due to, and can be relieved by changes in, our political leadership?
Perhaps so. Jesus is widely regarded as having compassion for the poor and suffering. But he also didn't seem to think there was much to be done for them in this world (and IIRC, throughout the New Testament, Jesus is practically the only person who ever directly helps a suffering person). Blessed are the meek -- but they'll have to wait to recieve their blessing in heaven. Even the acts of benevolence that believers are called to do -- sell everything and give it to the poor -- can be read more as ways of demonstrating one's faith (and hence preparing onself for the next life) than as aimed at producing good results for the recipients in the here and now.
Maybe Jesus is just a glory-hog. He doesn't want any humans -- even humans acting in his name -- to get credit for the improvements they make in the world. Instead, we have to wait for Jesus to do it himself. Maybe, being a timeless being, he only cares about whether things turn out OK in the end (after all, he took his sweet time in getting around to being incarnated and crucified after the Fall made that somehow necessary).
Or maybe, being a person in a premodern society who we know through the writings of other premodern people, Jesus simply had a very naive social theory behind his preaching. Today we easily understand the great variety of possible social orders that can exist, since we know about diverse cultures all around the world, and we've lived through major history-altering social changes. We're aware of the possibility of society being altered so as to be far more, or far less, just. But in premodern times, people were not so aware of the social possibilities. The way their own society was organized seemed to be pretty much the only way to do things. You could have a good king or a bad king, but they pretty much did the same things (and in those days the king had far less direct influence over daily life than modern governments).
Not caring who Caesar was may have made sense in Jesus' day. But insofar as apoliticism is a genuine element of Christianity, I find Christianity lacking.