A common argument by theists is that atheists, because they lack a thousands-year-old book with rules, are violent. This is both untrue and, in fact, the reverse.
Every once in a while, a theist in a debate may claim that atheism is immoral, or that atheists are monsters. This is demonstrably untrue. An oft-cited statistic is from here, and claims that atheists are less than 1% of the prison population. 150 prisoners out of 93000 identify as atheists? That can't be right. Estimates put the atheist population in America between 5% and 15%, sometimes even being so bold as to suggest 20%. Furthermore, there are more scientologists on that list that atheists. So those statistics simply won't do.
The UK government's archive website has a handy table showing the number of inmates by religion and the type of crime. Of a total of 64711 prisoners, 20739 are atheists. That's just under a third. Anglicans represent just a slightly smaller group of prisoners. All christians combined number 34657, about 53%.
Annual surveys by the British Social Attitudes Information System suggest that, in the past few years, about half of their population has identified as nonreligious. That means that atheists are only 3/5ths as numerous in british prisons as in the general population. Christians make up about half of the total population as well, but they are rather fairly represented in prisons.
What does this mean? It means that, contrary to the claims of many theists, atheists are not immoral, crime-prone monsters. In fact, atheists commit fewer crimes than theists. There are actually two possible explanations for this. The first I have already stated, that atheists commit fewer crimes. The second explanation would be that atheists are intelligent enough to get away with crimes, particularly, as shown on that handy table, sex and drug related crimes.