"having forgiven us all our trespasses, by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross. He disarmed the rulers and authorities and put them to open shame, by triumphing over them in the cross"
In writing about the record of debt that stood against us, and the powers and authorities that we battle against, Paul is acknowledging their reality. Paul is acknowledging the existence of sin and evil in the world, and their power. His encouragement isn't that they don't exist, but rather that they have been dealt with. They have been COMPLETELY defeated. The record of debt stood against us in that it brought condemnation. It is the record of debt that calls us 'sinner', 'law breaker', 'criminal'. The record of debt that rightly says we deserve death. This debt was true. Also, the rulers and authorities of evil are real. They once had dominion over our lives. We once belonged to them. We were once their slaves.
But thanks be to God, that through the cross, there is no more condemnation. Christ took the record of debt that stood against us and nailed it to the cross. The righteous punishment that we deserved for our law breaking, for our sin, for our wickedness, Jesus took. He absorbed the legal debt that stood against us. Jesus took the punishment of condemnation so that we could be free from its grip. More so, through the cross, the power of sin has been completely defeated as well. The word that Paul uses for 'disarm' renders a meaning of 'completely stripping something' or a 'complete disarm'. In other words, every power that sin had over us in our former life, has now been COMPLETELY STRIPPED. In his death and and resurrection, Christ's victory was so decisive, so complete, that Sin, that once powerfully ruled us and had tyrannical dominion over our lives, is now put to open shame, stripped naked of its power, and displayed publicly as defeated. This victory was decisive. It was complete.
Also, when we ponder the way in which God accomplished this victory (the cross), we can see how great His love is for us. The Son, though being infinitely powerful, became man, subjected himself to life on earth, and emptied himself of power, being hung on a cross. He became powerless, in order that through faith in him, he could empty sin over its power in our lives. On the cross, Christ became a curse, taking the punishment of a condemned criminal. He did this, so that we, being condemned criminals, could be free. Lastly, Christ died the most shameful death, being put on public display on the cross, in order to defeat the power of sin in our lives, and put sin to open shame by publicly displaying it as defeated.