Paul had God's authority to speak the truth.  But he was careful in applying that authority in pastoral situations (2 Corinthians 10:1).  He knew that each individual's response must be out of personal conviction, based on a clear understanding of the facts.  He had no wish to perpetuate the oppressive authoritarianism of the religious cults.  Paul was not a religious tyrant or dictator.  Such people can only operate if their demands are backed by force.  

Paul portrays himself as weak because he is physically old, and incapable of enforcing any demand because he is in prison in Rome.  However, his frailty and distance from Colossae could not stop love.  That was the Jesus-way too.  He spoke the truth but never forced people to follow or believe.  He forgave sins and grateful people loved Him (Luke 7:47).  So, Paul appeals to Philemon on the basis of God's sacrificial love which changes lives (1 John 4:20).

Onesimus, the run-away slave, had found Jesus through Paul's teaching while in prison.  How, we do not know.  But Paul wanted to prepare his master, Philemon, to welcome his truant back home without punishment and with forgiveness - not just as a slave but also as a brother in Christ.  This was not just a naïve and sentimental thought (Christians are sometimes rightly accused of that): there was real evidence of repentance (Matthew 3:8).  Instead of resenting God's Word and God's people in Philemon's home, he was hungry to be taught and loved other believers as a brother in Christ (Philemon 1:15-16).  Instead of refusing to serve, he was glad to attend to the old apostle's needs.  The Lord had changed his heart, from being useless to being useful.

Reconciliation without repentance has no integrity.  But where repentance is seen, the door should be open to forgiveness and reconciliation. This is no political or pragmatic business compromise; it is God's grace at work in the church of Jesus Christ (2 Corinthians 5:18-19).  Repentance is the key.  And part of that repentance is willingness to submit to the authority you once despised.  When that is seen worked out in sacrificial service, we should welcome what God is doing and restore the sinner; that is love in action.