That is why,in the christian bible there are 2 books New Testament and Old Testament.The Old Testament describes how God made the world ,Adam and Eva and what happened to the chosen people till the day that Jesus was born.The New Testament describes the life of Jesus and the new rules that are given to the chosen people....so the Christians must respect the New Testament were is no slavery and Jesus says to turn the other chick when some one slap your face.
http://biblehub.com/matthew/5-17.htm"Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to fulfill. 18"For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass from the Law until all is accomplished."