It seems that in his new More 4 TV series Dawkins claims that the reduction in violent crime is the result of the decline in the Christian faith, he says that as logic and intellect increases so does voilence. I am not sure on what figures Dawkins bases his argument as violent crime remains on the increase.
If you take the long view, which is based upon police records, the trend for violent crime is very dramatically upwards. In 1898 (when the majority of people in the UK believed in the existence of God and church pews were almost full) there were just over four thousand recorded violent crimes. That level was fairly steady until the Second World War and remained well under 10,000 a year until 1942. After the war (WWII) came the sustained upsurge, reaching 20,000 in 1950, and 30,000 in 1957. Even if we take the last 50 years: we still see an increase from 37,710 in 1960 to 979,502 in 20010/11 for England and Wales. (Scotland has a different system).
We need show caution because of a change in the way violent crime was recorded in 1998, plus a smaller change in 2002/03. Allowing for those changes, we see a 26 fold increase reducing to something like a near 13 fold increase. Either way, that is a massive, massive increase. We could better make a case for there being more violent crime in the UK as adherence to a faith has diminished. It would be interesting to plot these increases with church attendance over the same or similar period.