Interesting question, don't you think?
Well, I'll get straight to it. In a sense we are free to sin, and in another sense, we aren't.
You see, we are no longer under the law, and where there is no law, the Bible says, there is no transgression. How can I be guilty of sin if I am not under the law? So then I could indeed use my freedom as an opportunity for the flesh. I can not out-sin the grace of God. Period. So, in a legal sense, I am free to sin.
But Paul also tells us something else in Romans chapter 6. He makes the point that since we have died with Christ, we have also been rasied with Him, in the spirit. He made us new creations by way of His death and resurrection. We, when we believed the Good News, were made dead to sin through His death, and were made alive to God through His resurrection. So now, in my spirit, I am (humanly speaking) a slave to righteousness. Whereas I used to be a slave to sin, I am now a slave of righteousness. So, in that sense, I am not free to sin because it is no longer my nature to sin. John says no one who abides in Him keeps on sinning because God's seed (Jesus) abides in him. Jesus destroys the works of the devil, we don't. It is not by our struggling and striving, but by His work. His seed abides in us and He causes us to walk in His ways. For a Christian to live in sin is like a fish out of water. It isn't natural, and sooner or later he is going to stop. Peter tells us that the Christian has been made a partaker of the Divine nature.
We, who were diseased trees before Christ came, naturally bore bad fruit. The root determined the fruit. Identity and result. I could not be a healthy tree by trying hard to bear good fruit. "A diseased tree cannot bear good fruit". But in Christ, I have been made a new tree; a healthy tree. And Jesus says of us, "A healthy tree cannot bear bad fruit." Why? Because he is healthy! It's nothing to do with how hard he tries or a law he is under. It is his nature to do good.
So why not stop all the sin and behavior focused sermons and just proclaim the cross and resurrection of Jesus Christ, and what He has already accomplished!? You are a saint! There is no need to try hard to make yourself into someone you already are! Just rest and abide in Him! How do you abide in Him you ask? Well, how did you get in Him to begin with? By faith. Faith in what? In the finished work of the cross and resurrection! So how are you now to walk? The same way you were saved! Hello! "Having begun by the Spirit, are you now going to perfect yourself by your flesh?"
The law was part of an Old Covenant and what is old is passing away and has now become obsolete. And forget about "balancing" two covenants that are contrary to one another. The Old is obsolete. It isn't just an 'upgraded covenant'. It is a NEW Covenant.