The wisdom that Paul had as well as experience with sin led him to have a lot of insight when he was teaching the saints in Rome in his letter to them.
In the beginning verses of chapter 6, he teaches that sin must be abandoned with our old lifestyles before we are to be baptized. Baptism is the symbolized death, burial, and resurrection of Jesus, so when we are baptized, our old life dies and is buried while we are reborn anew in Christ, for only he can save us from our sins. Because of that particular symbolism, the method of sprinkling doesn't do it justice as a method of baptism because it takes on the appearance of a mere shower, not the resurrection of Christ as it was intended to be.
When we are reborn in Christ, we maintain the "newness of life" as Paul describes. This means that we should live our lives by His example and live as pure as we can, for Paul taught the Romans that "our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin." (Romans 6:6)
Thus, true freedom lies in serving God faithfully and living by His commandments and principles of the gospel. God is all about freedom, while Satan is all about slavery.