This passage is part of Luke's "sermon on the mount" and it is the part where Jesus teaches us to love our enemies. It's not likely that Jesus is telling us to have warm feelings towards people who hurt or threaten us! Rather, he seems to be calling us to an attitude in life. Rather than bargaining (I'll love you if you love me; I'll do good for you if and only if you do good to me) Jesus is teaching us to add goodness into the world at every opportunity. This will take some wisdom, care, and good boundaries, but... is it possible to be constructive and work towards the good of others -- even with our enemies?