How do you deal with someone who says, "I'm Basically a Good Person"? Here's one approach.
Try this calculation with them. If you sinned only ten times a day from your tenth birthday to your sixtieth--and keep in mind we're not just talking about rape, pillage, and murder, but the full range of human moral failing, including heart attitudes and motives--only, ten sins a day, what would your rap sheet look like? You would have amassed 182,500 infractions of the law. What judge in his right mind would turn you loose with a record like that?
Whenever you're tempted to trust in your own ability, take a good look at the standard, God's Law, then look at your own score card. To use Paul's words, the law has each of us "shut up under sin" (Gal. 3:22), it's closed our mouths, and we all have become accountable to God (Romans 3:19). Saved by our own goodness? The Law gives us no hope.
Hat tip: Stand to Reason Blog by Gregory Koukl on 3/18/10