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.
The “size” of a sin is not ultimately determined by the sin itself, but by the one who was sinned against. Sin is infinitely wicked because it rejects the one who is infinitely holy and good. The more we recognized the perfection of God’s holiness, the more obvious this truth becomes.
In general, we may say that some sins have more harmful consequences than others if they bring more dishonor to God or if they cause more harm to ourselves, to others, or to the church. Moreover, those sins that are done willfully, repeatedly, and knowingly, with a calloused heart, are more displeasing to God than those that are done out of ignorance and are not repeated, or are done with a mixture of good and impure motives and are followed by remorse and repentance (Wayne Grudem and Jeff Purswell).
Though judgment applies in all these cases, it’s one thing for people with very little knowledge of Jesus to reject the Savior. it’s quite another for people that grow up in Christian family and are heavily exposed to the truth. It’s even quite another for someone to profess faith in Christ, appear to walk with Jesus and then give the Lord a vote of no confidence. And it’s even quite another to do all the above and then intentionally lead other Christians astray by false teaching (see Heb. 6:4-6, 10:26-27; 2 Pet. 2: 20-22).