To double the blessing to my adversary. To change my reasons for complying. To give me an opportunity to be with my adversary instead of against him. To change my focus from me to him. To give me an opportunity to turn an adversary into a friend.
Sinners love their friends.
They bless their benefactors. They often return good for good. They help the deserving and those who can reciprocate. In other words, positive stimuli prompt sinners' positive responses. The children of God love everyone, including their enemies.