A great article of the relationship between religious beliefs and niceness – Does Religion Make You Nice? – that raises some interesting issues:
Arguments about the merits of religions are often battled out with reference to history, by comparing the sins of theists and atheists. (I see your Crusades and raise you Stalin!) But a more promising approach is to look at empirical research that directly addresses the effects of religion on how people behave.
[...]
In Gross National Happiness, Arthur Brooks notes that atheists are less charitable than their God-fearing counterparts: They donate less blood, for example, and are less likely to offer change to homeless people on the street. Since giving to charity makes one happy, Brooks speculates that this could be one reason why atheists are so miserable. In a 2004 study, twice as many religious people say that they are very happy with their lives, while the secular are twice as likely to say that they feel like failures.
So religion makes you happy and you give more blood? Not so fast, writes Paul Bloom:
A 2005 study by Gregory Paul looking at 18 democracies found that the more atheist societies tended to have relatively low murder and suicide rates and relatively low incidence of abortion and teen pregnancy.
Not to give away the answer, but it’s all apparently about the community, not beliefs – it’s a great piece, worth reading in full.

