rejection of an eye for an eye - "do not resist an evildoer"; "turn the other cheek"; "go with him 2 miles"; "give to him who begs from you"
rejection of hate your enemy - "love your enemies and pray for those who persecute you"; "you therefore, must be perfect as your heavenly Father is perfect"
response to the Sermon on the Mount from those who accept Jesus' authority as God's authority:
Jesus is saying what God required them to do
although these expectations are a challenge to normal human behaviour e.g. to be "perfect", those who assume Jesus is teaching with the full authority of God take these teachings seriously
e.g. pacifism - not resisting those who might be enemies
response to Sermon on the Mount from those who accept Jesus' authority as only human:
regarding not resisting attackers: liberal Christians may point out the context in which Jesus was speaking - resistance to Romans could lead to crucifixion
some may say it is cowardly not to defend from an attack
some may suggests the request to be perfect is hyperbole - it is not an achievement of the impossible that is required, but an attempt