http://bible.com/8/luk.6.35-36.amp But love your enemies and be kind and do good [doing favors so that someone derives benefit from them] and lend, expecting and hoping for nothing in return but considering nothing as lost and despairing of no one; and then your recompense (your reward) will be great (rich, strong, intense, and abundant), and you will be sons of the Most High, for He is kind and charitable and good to the ungrateful and the selfish and wicked. So be merciful (sympathetic, tender, responsive, and compassionate) even as your Father is [all these].
While it is true (because the Bible says so) that you can’t make a wicked person righteous by being nice to them, it is always right to show kindness in love.
Our shedding abroad the love and grace of God is a natural result of receiving a new nature in Christ. The God kind of love never fails.
So, whether to a friend, or to an enemy, it is always our intent to bless and express the goodness of God.