See the article I just posted on Christian literalism, regarding your point about the "forensic quality" (link below).
This move of assimilating secularism to Christendom can seem a little cheap and reflexive, no? It's certainly that way in the hands of Christian apologists who mean to undermine secular society. The problem is that Christianity, too, can be traced to Hellenistic Judaism. So in finding the roots of philosophical atheism in Christianity, we could just as well be saying we're finding them in paganism, in the Greco-Roman traditions that Christianity drew on, such as Stoicism, Cynicism, and Platonism. It's just a question of where you want to stop looking in the historical continuum, which is often arbitrary.
I see the point of saying that secular society isn't as alien to Christendom as it may seem to zealous atheists. But we should be wary of saying that Christianity is foundational to Western cultures. Christianity is the syncretism of Judaism and paganism, so the roots go far beyond Christianity.
