So which is it? When someone blows it and sins against God, were they transgressing the law, or were they merely missing the mark? Well, it depends upon the situation. It comes down to differentiating between what are commonly called sins of "omission" and sins of "commission". On one hand, the sinner was trying his best to do what's right and didn't cut it, and on the other hand, he knew full well what he was doing was wrong and yet did it anyway.
These two types of sin are clearly depicted in the life of king Saul. If you remember in 1Samuel 13, when the Philistines were about to close in on Saul and his troops in Gilgal, while Samuel tarried, the men of Israel were afraid to the point of trembling and king Saul became impatient and made burnt offerings to the Lord, which was in disobedience to what the Lord had commanded. When Samuel did arrive, it was then that he pronounced the judgement of God on Saul for his sin. But Saul thought he was doing the right thing! He was offering to the Lord before the battle, but he didn't do it right, and God judged him for it. A sin of omission.
Then at a later time, the Philistines again arrayed themselves before Israel for battle, and Saul was so afraid "his heart greatly trembled". (1Samuel 28) By now Samuel was dead, and the Lord did not give an answer to Saul through the prophets, so he sought out a woman who had a familiar spirit. He went to the witch of Endor to find counsel. Here Saul knew what was right or wrong, and deliberately crossed the line and sinned against God. A sin of commission.
Sins of commission are like having a line drawn in the sand and stepping over it anyhow. Sins like, lying, theft, adultery, murder, gossip, envy, doubt, coveteousness, blasphemy, and idolatry. We all know these things are wrong and yet we do them anyhow.
When sharing the gospel with unbelievers, I usually don't spend too much time discussing sins of omission. Here's why: We've all heard the analogy of an archer shooting at a target, but missing the bullzeye, and this is "missing the mark", or "sin". This is a very poor analogy to use because it paints the picture that the sinner is trying his best to live right but just can't do it. In other words, he's not a bad person, he just needs someone to help him with the little he's lacking. Using this analogy to refer to his sins as "missing the mark" does nothing in terms of leading him to repentance because you're telling him he's already trying hard enough. It totally defuses the seriousness of sin. This also makes God look unjust for sending sinners to hell when they were doing their best to do what he says. Although we have all committed sins of omission, and missed the mark in that sense, it is more of a loss to the sinner rather than a gain to soften the blow by avoiding more obvious sin.
I know its hard not to let the fear of man get to us when sharing the truth of the gospel. Its hard to talk about sin and judgement, because we are afraid of how people will respond, but it is absolutely necessary in order for someone to understand the gospel. But what is the gospel? In a nutshell, we've sinned against God and deserve his wrath, but because of his love for us, he sent his Son to live and die for us so that all who will repent and put their trust in Him will have forgiveness of sins. What is more likely to make this good news good? Telling someone they are trying really hard but just need a little lift? Or gently and lovingly showing the sinner the enormity of his crimes? Once a person comes face to face with their sin and realizes that the judgement of God is just, then the blood of Jesus is something they will cling to for a lifetime.
They don't bail out on the Lord when times get tough. They didn't come to him for a better lifestyle, or to try something different. they came because they have sinned against God, and they need the blood of Jesus to cleanse them from sin. They don't wak away from him when they lose their job, or when their spouse fails them, or when they are tempted, or when the bank takes the house. No! These things only make them cling tighter to the Lord and even look forward to getting out of here.
So, boys and girls, don't be afraid to bring up the hard subjects. When witnessing, don't just gloss over the seriousness of sin, but show the person their great need of the Saviour. They will thank you for telling them the truth, because they sure aren't hearing it from many sources these days. The Lord will honor you for preaching the whole counsel of God. Don't you want to stand before him and hear "Well done, good and faithful servant"? Be faithful to proclaim the whole truth. Do it for the glory of God!