It's unwise to give an unrepentant sinner the message of God's forgiveness unless he shows some evident concern about his salvation. For example, lust is such a blinding and powerful sin, a man will not want to let it go unless he becomes convinced that it's in his best interest to do so. Hell is a very good reason to do so. So, use the analogy of lust being like a sparkling stick of dynamite in a child's hand. He loves the sparkle and holds it close with great delight. He doesn't realize that it will kill him. Lust sparkles before the face of the unsaved, but it will brings terrible destruction. The Bible says "it brings forth death." Without the understanding that he is in danger, sin will damn him. There goes another minute. Gone forever. Go share your faith while you still have time.