Essentially, the distinguishing mark of those who strive after Christian perfection is that they love the sinner and detest only sins.
When they must avenge wrongdoing, they do so, not with the cruelty of hatred, but with justice administered with moderation, lest forgiveness without satisfaction do more harm to the sinner than punishment. (emphasis mine)(Augustine, Against Adimantus 17, cited John E Rotelle, O.S.A, in Augustine Day by Day)
My thoughts had been running along the line of "turning the other cheek" which really refers to not returning evil for evil. The call to forgive is not a call to lawlessness; to disregard law and order. The Father upheld his holy Law by meeting out the punishment I deserve upon the Son while offering me forgiveness. So, pursuing justice may be the greatest kindness in the end. Justice upholds and strengthens the local community. The greatest challenge is to pursue justice with meekness and humility rather than with cruel hatred. Vengeance corrupts while justice seeks healing.