Here's the problem: when every sin is seen as the same, we are less likely to fight any sins at all. Why should I stop sleeping with my girlfriend when there will still be lust in my heart? Why pursue holiness when even one sin in my life means I'm Osama bin Hitler in God's eyes? Again, it seems humble to act as if no sin is worse than another, but we lose the impetus for striving and the ability to hold each other accountable when we tumble down the slip-and-slide of moral equivalence. All of a sudden the elder who battles the temptation to take a second look at the racy section of the Land's End catalog shouldn't dare exercise church discipline on the young man fornicating with reckless abandon. When we can no longer see the different gradations among sins and sinners and sinful nations, we have not succeeded in respecting our own badness; we've cheapened God's goodness. If our own legal system does not treat all infractions in the same way, surely God knows that some sins are more heinous than others. If we can spot the difference, we'll be especially eager to put to death those sins which are most offensive to God.
Kevin DeYoung