Since our righteousness is achieved by what Christ alone accomplished, we should be very humbled. Since it is by God's grace alone we ourselves have not been judged, this should prevent us from judging others. We should, rather, be interceding for those whom Christ died for as well. Whether friend or foe, we are to love all.
It is the love of the Father for us, by the presence of the Holy Spirit in us, that brings about a recognition of our own sinfulness. (John 16:8) He alone works repentance in us. (2Timothy 2:25) Confessing and embracing this, we then have the ability to turn this love towards others, becoming ambassadors for Christ.
Those who judge sinners whose hearts are repentant fail to understand that this repentance is the evidence of God's holy work in their lives. The love of God is not in those who judge. They are still blind and deaf.
"Therefore, I tell you, her many sins have been forgiven--as her great love has shown. But whoever has been forgiven little loves little." (Luke 7:47) Our love for others is proportionate to the degree in which we perceive God has forgiven us.
God's love for the world manifests itself when His children know they have been saved from themselves and become resurrected into the life of Christ; no longer living to themselves, but to Him who has called them to go in the same manner of love that He came; Immanuel...God with us.
"All this is from God, who through Christ reconciled us to himself and gave us the ministry of reconciliation; that is, in Christ, God was reconciling the world to himself, not counting their trespasses against them, and entrusting to us the message of reconciliation. Therefore, we are ambassadors for Christ, God making his appeal through us. We implore you on behalf of Christ, be reconciled to God." (2 Corinthians 5:18-20)