This series is meandering a little bit at the moment - but that's OK, I know where it's going to end up and all these byways are fertile. However, that Peter Hitchens' piece has provoked so many comments that I thought I'd put in something a bit more explicit (I've also been commenting fairly heftily on Stephen Law's site, in response to his posts). Click 'full post' for text.
Can an atheist be good? Obviously, I know lots who are.
The more interesting questions are: 1. does the social acceptance of an agreed framework of values tend to enable people to be good or otherwise? And: 2. does atheism undermine the social acceptance of an agreed framework?
(I think this was Peter Hitchens' essential point - that it is the breakdown of common belief that has undermined social virtue. It happens to have been Christianity in the British context, but it doesn't need to be.)
In answer to question 1. I would say yes. Without a common agreed framework within which society can function you end up with a more or less violent social order. You need an agreed framework of values, and you need that framework of values to be legally enforced, in order that the highest levels of human flourishing can be reached. If there is no agreed framework then there is simply an imposition of violence, either from a central authority to coerce obedience, or between more or less strong groups and individuals. (I think this is Milbanks' point about the ontology of violence.)
Note: this common agreed framework does not have to be Christianity, it does not even have to be theistic - it can definitely be atheistic, as with China (for the time being).
In answer to question 2. I would say that - again in the British context - atheism has undermined the social order, and to this extent I would agree with Hitchens. This is not a point about individual atheists, it is that there needs to be something outside of the individual conscience to which appeal can be made. The individual conscience is not the final arbiter of the good, or, put differently, the individual conscience needs to be educated into social norms.
As I understand it, atheism doesn't (cannot) recognise anything outside of the individual conscience to which appeal can be made. From a (humourless) atheist point of view, for a common social order to be established, each individual member of the community needs to be intellectually persuaded of the merits of that order. The individual conscience is the lynchpin of the system, around which everything else pivots.
What this misses out is the panoply of ways in which human beings operate non-rationally (note, NOT irrationally) on which their rationality depends. You could say that atheism has a hopelessly inadequate anthropology. In particular, choosing of the good depends upon evaluation, which is a form of emotional intelligence. Why shouldn't I have that extra portion of chocolate dessert? Why shouldn't I lie and cheat and steal and so on?
The Christian answer to those questions is not, ultimately, that they are "wrong" but that they are incongruous with our deepest desires - our deepest desire being, in the end, to be united with God. The rules and regulations (eg the Ten Commandments) are guidance to teach us about ourselves, and to indicate how we can best flourish.
I think atheism has destroyed this conception. Or, to phrase that more precisely, I see atheism as one aspect of Modernity, and Modernity has destroyed this conception. We are 'after virtue'.
I am very interested to hear atheist perspectives on the two questions above.
UPDATE: What John Michael Greer (a druid) writes here is relevant to the overall point.