Michael Craven recounts how Christianity won a culture war:
The Roman world was brutal and generally indifferent to suffering. Sympathy and mercy were weaknesses, virtues anathema to those of Rome. The ancient world was both decadent and cruel. The practice of infanticide, for example, was widespread and legal throughout the Greek and Roman world during the early days of Christianity. In fact, abortion, infanticide, and child sacrifice were extremely common throughout the ancient world.
Cicero (106-43 BC), writing in the period before Christ, cited the Twelve Tables of Roman Law when he wrote, “deformed infants should be killed” (De Ligibus 3.8). Similarly, Seneca (4 BC-AD 39) wrote, “We drown children who are at birth weakly and abnormal” (De Ira 1.15). The ancient writer Plutarch (c. AD 46-120), discussing the casual acceptance of child sacrifice, mentions the Carthaginians, who, he says, “offered up their own children, and those who had no children would buy little ones from poor people and cut their throats as if they were so many lambs or young birds while the mother stood by without tear or moan” (Moralia 2.171D). Polybius (ca. 200-118 BC) blamed infanticide for the population decline in Greece (Histories 6).