One of the most difficult requirements/expectations of the Christian life is being kind to those who mistreat us. The principle is stated most clearly in vss. 27 and .35, “Love your enemies.” That’s what Jesus is calling us to do here—to be nice to those who are not nice to us, to respond with kindness when others mistreat us. That is truly difficult.
Our natural tendency is to do just to opposite—to treat others in the same way they treat to us.
Jesus calls us to act against our sinful nature—to respond to hostility with kindness, to show love to the wicked, and to be merciful to the abuser. Vs. 35end: “[God] is kind unto the unthankful and to the evil.” That’s the reason we must treat others as we would want to be treated.
Our passage is part of the Sermon on the Plain/Mount. Jesus is describing the attitudes and actions of those who will enjoy a place in the kingdom of God. I.e. he’s describing what he expects from those who claim to follow him. If you claim to be a Christian, these attitudes and actions should be true of you.