I often get frustrated when trying to get people to understand grace because I try to prove it to them by theological debate, desiring to show them that I am right and they are wrong. I believe this is the wrong way to approach people. I think we are to give them grace at their level. I don't mean they're dumber than we are, I just mean that we need to get to the heart of grace rather than trying to show them why grace is right and mixture isn't. Rather than trying to persuade them to accept that what I am saying is true, I need to recognize their need of grace and just give it to them.
Sometimes people don't need a well laid out argument for grace, though that does indeed have its place, but sometimes people just need to hear something as simple as, "God isn't mad at you." I need to see the heart of the person that I am speaking to rather than wondering how I can make them believe the truth about grace.
I guess my point is that we don't have to have the most persuasive arguments, though we do indeed need to be able to back up our claims with the Scripture, but we just need to get real with people and get to the point: The Cross of Jesus Christ has provided forgiveness of their sins once for all, not through their repentence or even their faith. Our faith doesn't forgive our sins, our faith receives our forgiveness. Forgiveness is already there. It has been here since the Cross, but now all we have to do is reach out and take it. So the message is simple: Return to God, He has redeemed you. You're forgiven! Take it while there is still time!
I do not deny the coming of judgment for unbelievers, but it won't be because they were not forgiven. It will be because they did not believe the Good News that was spoken to them, not because they sinned. No human being goes to be with the Father because they didn't sin. They go to be with Him only by the righteousness provided for them through Jesus Christ.
Your sins are taken away, they are removed, they are washed, and cast as far as the east is from the west. Jesus bore all the wrath of God against sin and no one will ever be judged because they sinned, but because they rejected the gift Jesus bought for them. They will go to hell because they insulted the Spirit of Grace, by counting the precious Blood of the Covenant as an unholy thing. They go because they sin willfully after receiving the knowledge of the truth. They persist in unbelief even after someone has proclaimed forgiveness to them through the Cross and through no merit of their own. For that hardness of heart there is no excuse.
It is bad enough to sin even after hearing God's law, but it is even worse to reject the free gift of forgiveness for that sin. Everyone who disobeyed the law of God died without mercy on the evidence of two or three witnesses. How much worse punishment do you think will be deserved by the one who has rejected God's own Son after everything He went through so that you could be brought back safely to God? It is the religious, not the filthiest sinner that will receive the harsher judgment.