The basic problem is that we are fallen. All religious, politican and moral systems are attempts to cope with that. (Christianity claims to be the system wherein we did not come up with the answer but rather God proactively solved the problem for us by bearing sinful humanity to the cross and raising it from the dead to new and divine life in christ.)
Atheism copes with our fallenness by pretending it’s not true, all while maintaining a moralistic critique of theism that puts *enormous* weight on the reality of sin. However, it blames the sin on God, not man and fallen angels. In its utopian forms, it sets out with missionary zeal to perfect man and inevitably turns to violence (because atheists are, you know, fallen anyway no matter what they say) and then has to tell a bunch of lies to cover up its crimes. Fr. Oaks dissects the lies.
Not, of course, that Christianity asserts that Christians are without sin. On the contrary, it warns of the possibility of damnation even for Christians if they do not abide in Christ (for which atheism irrationally curses it, like a patient cursing a doctor for “threatening” pneumonia patients with death if they do not finish their course of treatment).