Law before Gospel?

Recently as I have been reading I have crossed a common thread, especially among reformed writers, that in order to effectively reach unbelievers with the gospel we must first use the law to expose their sin.  They say that without knowledge of sin there is no need for a savior.

Ray Comfort and Kirk Cameron have a popular show on television called "The Way of the Master" that shows how this method can be used to reach people with the good news of Jesus Christ.  Basically it works like this:  you quote each of the Ten Commandments one by one and ask the person if they have obeyed each commandment perfectly their entire lives.  When they answer "no" then you are able to show them that by their own admittance they are a "God hating, adulterous, liar or a idolatrous, thief and coveter..." whatever the case may be.  Now they are primed to hear the gospel that Christ came to save us from our sin.  But is this the way of the master?

In Luke 10 Jesus is confronted by a lawyer and tested.  Jesus asks the man "What is written in the law?  How do you read it?"  After he answers Jesus said to him "You have answered correctly.  Do this and live."  So clearly Jesus did use the law to show the source of eternal life (the lawyers original question).  Yet earlier in the same chapter of Luke's gospel Jesus sends out the seventy-two.  Here is what He instructs them to do:  "Whenever you enter a town and they receive you, eat what is set before you. Heal the sick in it and say to them, ‘The kingdom of God has come near to you." (Luke 10:8-9 ESV)  No mention at all of the law only to speak and show that the Kingdom of God is near.

If the way of the master is to preach the law before the gospel then Paul directly contradicted this in 1 Cor 9 where he writes:  To the Jews I became as a Jew, in order to win Jews. To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law. To those outside the law I became as one outside the law (not being outside the law of God but under the law of Christ) that I might win those outside the law. (1 Corinthians 9:20-21 ESV)

So then the law is a good evangelistic tool for those who are already trying to follow the law but not for those who are without knowledge of the law.  If that is the case then evangelistic methods that put the law before the gospel in order to reach non-Jews aren't the way of the master.

We should preach Christ and Him crucified.  We should seek to put Jesus on display through our words and deeds.  When unbelievers see the body of Christ, when they are given a revelation of who God is, when they see him high and lifted up, when they see his glory in the face of Jesus Christ they will be convicted of sin.  They will know their need for him.  The law may bring us to the knowledge of sin but it is ineffective to bring us to a knowledge of Christ.  It is not necessary to bring someone to the knowledge of sin through the law, that knowledge will come as they are shown the glory of Emmanuel.

It is the Holy Spirit that convicts us of sin and He does so through a revelation of Jesus Christ.  Jesus told his disciples:   "And when he comes, he will convict the world concerning sin and righteousness and judgment: concerning sin, because they do not believe in me; concerning righteousness, because I go to the Father, and you will see me no longer; concerning judgment, because the ruler of this world is judged." (John 16:8-11 ESV).