To the detached observer, it does look very much like RA's audience recognizes a link between an attempt to live a more moral life and theism. That's why they accuse RA of becoming a believer, despite the fact that he has simply been attempting to live out natural virtues that would have been no mystery to Aristotle. If you can be a good person and an atheist, why would they make this connection so automatically? And even more, why would they reflexively *hate* the attempt at virtue (an attempt made, so far as I can see, without any recourse to God)? This brings us to the next point: which is that hard atheism is *essentially* negative.
I believe one can be an atheist and a good person, of course (or a follower of a different religion than Christianity); as Mark points out, the classical virtues were propounded independently of religion. But Mark is also right to note that the suspicion with which many "hard" atheists view attempts at virtue is telling -- maybe there is something to the link between faith and virtue. That's certainly something that Christians believe, in any event. I hope RA doesn't let his commenters dissuade him from his aspirations to virtue, regardless of whether he does come to believe in God. (But I can't help but hope that also follows.)