One of the paradoxes of history is the relationship between the beliefs and the practices of the early Christians as compared to those of the culture around them.
The Greco-Roman world's religious views were open and seemingly tolerant - everyone had his or her own God. The practices of the culture were quite brutal, however. The Greco-Roman would was highly stratified economically, with a huge distance between the rich and poor. By contrast, Christians insisted that there was only one true God, the dying Savior Jesus Christ. Their lives and practices were, however, remarkably welcoming to those that the culture marginalized. The early Christians mixed with people from different races and classes in ways that seemed scandalous to those around them. The Greco-Roman world tended to despise the poor, but Christians gave generously not only to their own poor but to those of other faiths. In broader society, women had very low status, being subjected to high levels of female infanticide, forced marriages, and lack of economic equality. Christianity afforded women much greater security and equality than had previously existed in the ancient classical world. During the terrible urban plagues of the first two centuries, Christians cared for all the sick and dying in the city, often at the cost of their lives.
Why would such an exclusive belief system lead to behaviour that was so open to others? It was because Christians had within their belief system the strongest possible resource for practicing sacrificial service, generosity, and peace-making. At the very heart of their view of reality was a man who died for his enemies, praying for their forgiveness. Reflection on this could only lead to a radically different way of dealing with those who were different from them.
-- p. 20, The Reason for God by Timothy Keller