Peter Leithart's Against Christianity

I received Peter Leithart's latest for Christmas, and since I am a big fan, am doing a review. Here are some online reactions I read to give me an idea of what I was getting into:
http://www.amazon.com/gp/product/1591280060/qid=1135644116/sr=2-1/ref=pd_bbs_b_2_1/103-9444830-8792624?s=books&v=glance&n=283155
One of the things I have consistently been leery about since my involvement in the Reformed movement is "Christian Reconstruction". To me, it sounds uncomfortably something like the concept of jihad, minus the meanness. It's only fair my reader knows my presuppositions before he reads the review, so here are some more reservations. Credenda/Agenda (Leithart is their resident scholar) is often too combative, too critical, and just too ornery for my tastes (though I agree with them a great deal). On a more serious side, I do have serious reservations about their rejection of "Modernity" and "Postmodernity" in favor of what they would like to call Medieval Protestantism (something that never existed, and for good reason). In otherwords, they tend to overrate the ancients and never read the moderns, in my opinion, or to be ignorant of them altogether. This, I would say, is not, on balance, a good thing. But this is not unique to them, and, to a degree, characterizes all Reformed intellectuals. Anyone who thinks they can skip the Modern sequence of Kierkegaard, Nietzsche, Rosenzweig, Barth, Bonhoeffer, Spengler, and Rosenstock-Huessy (to name the Teutons), or some similar sequence in Anglo or French thought, has got another think coming. They will reinvent the wheel, ineluctably. But I haven't finished it, so this will be an ongoing arguing with myself, and whoever else deigns to join in.
So far, this is my impression:
I am on page 36, and already he has picked a fight with Paul Tillich for saying that "culture is religion externalized" (and so implying that the Bible is a book of morals and religion, and not politics or culture). Au contraire, demurs Leithart, Paul chose the word ekklesia because that was Aristotle's word for the lawmaking assembly of the polis, thus implying that the Church (Ekklesia) was a rival and potent polis who was subsuming or replacing the ancient polis. He wants to argue that Christ did not found a competing religion called "Christianity" (why he didn't just call it Churchianity, I am not sure), but instead a replacement City of God to supersede the City of Man. I am wondering aloud if this was Augustine's thesis, and will have to check with Ben House.
What he wants to say is not that Christians ought to be involved politically, but that they can't help but go beyond "involvement" into replacement. Thus, Saint Paul would say it is a shame to go to the pagan law courts with Christian disputes. "I tell you boys what," says he, "let the weakest, most immature Christian decide. He will do a better job." Now I would agree with Dr. Leithart that the project of Christendom failed in Europa (mainly due to the retainment of self-glorification and tribalism which became nationalism, all under the auspices of the Catholic Church). But I get the distinct impression that he thinks that this would entail some sort of out of hand rejection of pagan categories of thought, which would seem to kind of undermine the whole idea of Saint Paul's argument, phrasing it, as he did, in the language of Aristotle. Supernature perfects nature, but in perfecting it, will not obliterate it. Thus, the statecraft of Bismark, the philosophy of Nietzsche, the sociology of Rosenzwieg, the heroism of Churchill, et al are valid. Science, politics, and other activities are not sealed doors to pagans. Einstein, precisely because he wasn't Christian, may have insights and achieve discoveries that are sealed to Christians, who, I demur, are committed to other more important pursuits. This is not to say that someone like Reimann might not do a great deal of good scientifically due to his faith.
But it does seem to me that Leithart is throwing out the baby with the bathwater. I do not want to say that Christ is not Lord over Science. But it is undoubtable that pagans, in God's grace, are used and used up to achieve many things that Christians are spared the agony of uncovering (one thinks of the antique Danish heroism on the Eastern Front of World War II). And that, also undoubtedly, pagans deserve their share of glory and justice in these pursuits. I think it specious to imply that the Ekklesia is to be a rival polis. Better theologians have debated this, in fact, than myself or Leithart (Karl Barth, von Balthasar, Rauschning). And this sort of thing, I think, has been tried by men just as pious, intelligent, and dedicated as we, and it ended in the Christmas true of 1914. America, indeed, is built, not upon the idea that we are a Christian nation, but upon the idea that it is possible for everyone to participate in the justice, equity, and mercy of God. The liberalism of the West, I believe, is not invalid, nor is it futile. To say otherwise, I think, places oneself outside of the Western tradition and certainly outside of the exceptional American experiment.
It may be that we Americans will have to leave our individualism, just as our European ancestors came across the seas in baptism, and fled their tribalism. But, for now, we remain the last, best hope of earth. Such is not to be cast aside lightly, nor in the name of even faithfulness to Christ. I may be reading into Leithart, so I will continue this review and modify my conclusions, perhaps.