Since the introduction of capitalism and free market, which marked the start of large income inequality, Chinese society has definitely experienced higher crime rate, lower civic participation, lower social cohesion, etc.

http://en.wikipedia.org/wiki/Social_issues_in_China#Overview

I remember when my home city was still very poor, people treated each other much better. There is a general sense of community and trust. People are always offering a hand to those in need of help, even though helpers themselves are poor. Theft was literally unheard of, let alone more serious crimes.

Also Edwardian England is a compelling counter-example. Read "The Classic Slum" by Robert Roberts. British society around 1900 was massively unequal and lots of people were desperately poor. But their homicide rates were 100X lower than the rates seen in the contemporary ghetto. The poor working class areas of England during that period had intact families, schools that provided discipline, strict policing, and strong institutions.