I have often heard people argue the 'good without god' point with christians. Many atheists are outraged by the question "So why are you good?" Personally I find the question to be more risible (and indeed ignorant) than offensive. However, I understand that for some of us atheists it is a useful rhetorical counter-argument. It can be an opportunity to turn the table on theists who normally seem to claim the 'moral high ground' of being offended as their own.
It is interesting to see the way that some decent god-fearing people assure their atheist protagonist that without god there would be nothing to stop them stealing, raping and murdering. I have heard peaceful people expressing surprise that atheists in general do not feel a need to indulge in criminal activities.
In one report which is easily found on the web, but difficult to verify, I read that 75 percent of Americans are 'God‐fearing Christians'; 75 percent of prisoners are God‐fearing Christians. 10 percent of Americans are atheists; 0.2 percent of prisoners are atheists. That sounds like good evidence for the atheist point of view if it is actually true, but to be honest I tend to be skeptical about the claim. I think it seems most likely that one of the statistics dates from a 1925 survey of prisons, and that the rest has become an internet meme after some mischief on a web site. (Please correct me in the comments if I am wrong.)
However, even if you assume that the data is true, I wonder what this statistic really means. Is this the figure for people who are in the process of going into prison, or the figure for people who are already coping with the obvious difficulties of prison life? I'm not so sure how I would behave if I found myself in that situation, but I suspect that I would answer the question differently in the two cases. Once in the prison I think I would want to do everything possible to avoid standing out from the crowd. If that meant pretending to be christian again, I think my conscience would not prevent me from such a claim!
Would god forgive me for such duplicitous behaviour? Strangely enough I don't worry about that too much.