But verse 18 shows us that God was still merciful because He said,"Come let us reason together, though your sins be as scarlet, they will be as white as snow, though they be as red like crimson, they will be as wool." God was telling them that if they would repent of their sins, He would forgive them. God cannot stand sin but He will not turn anyone away that comes to Him for forgiveness.
Many people are living the same way today. They are living moral lives. They don't swear, drink or gossip, so they feel that they are living good lives. But without Jesus, their lives are being lived in vain, regardless of how good they feel they are. If this is you today, come before God with a honest heart and repent of your sins. He will forgive and restore you.