I think that the term has more to do with entering into a controversy between the sinner and God. The sinner that is unrepentant in a way judges that his action is good therefore judging God and His Way as inferior. This is the meaning of God being justified in His Words. God will not be judged in the way we think about it as far as man will be judged; but when we oppose God, we judge Him, which is really silly because without God we are nothing and will die in our sins, hence Holy David’s plea for forgiveness and cleansing of his sins.
Like others have mentioned, it is also a foreshadowing of Christ’s Incarnation, Death, and Resurrection, because it is the sins of man that enslaved us to Sin, Death, and the Devil because we judged God’s Way to be wrong. We followed after the Devil’s temptation even though we had everything we needed and had no problem choosing to reject God’s command to abstain for a time from the Tree of Knowledge of God and Evil. We all since then have committed the same sin of choosing the Devil and our own Ego over God. God in His Love has made the most effective method of salvation for us by bowing the Heavens and becoming man and destroying sin and death in His flesh so that we can share in this victory if we are recreated and put on Christ in Baptism and imitate His Holy Life. Christ triumphed over the judgment that put Him to death and His Words are justified as being Life. The wicked have been shown that they reject the Light and prefer the Darkness, and that they have been conquered and will be finally sent off into isolation at God’s final Judgment. In the meantime their existence is useful for those that will become Righteous in various ways.