Kevin DeYoung (in The Hole in our Holiness) discusses the crucial importance of recognizing that some sins are more sinful than other sins:
As R. C. Sproul puts it, “The idea of gradation of sin is important for us to keep in mind so we understand the difference between sin and gross sin.” All our sins are offensive to God and require forgiveness.
But over and over the Bible teaches that some sins are worse than others.
The Mosaic legislation prescribes different penalties for different infractions and requires different sacrifices and payments to make restitution.
Numbers 15 recognizes the difference between unintentional sins and those done “with a high hand” (Num. 15:29–30).
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-n-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 Lands’ 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.
DeYoung, Kevin (2012-08-07). The Hole in Our Holiness: Filling the Gap between Gospel Passion and the Pursuit of Godliness (Kindle Locations 1060-1066). Good News Publishers. Kindle Edition.
markchanski 
A thought on this, dear friend. We can potentially be speaking out of both sides of our mouth on the issue when addressing unbelievers if we take this truth too far. Although not all sins are the same and have different earthly penalties and consequences – there may be a danger on both ends of the spectrum. Seeing all sins as “equal” is unhelpful to the believer for the reasons you listed. Seeing sins as “unequal” may lead us down two additional dangerous paths: 1) seeing the log in our brothers eye and believing we only have the sliver, or 2) ignoring the equal spiritual consequences of all sins (small and great). It is true that some sins will have greater consequences on earth and may have very different needs for restitution, but the heavenly sacrifice needed (the death of our Savior) for both small and great sins was the same. The eternal judgment deserved by any who do not lead a perfect life is the same. If we find our hearts are prone to judge a brother or sister more harshly than ourselves, or if we misunderstand the concept of sin resulting in death – we must root ourselves again in a balanced understanding of the truth you described. We must remember that the fall of man through eating of forbidden fruit might be seen as a ‘small’ sin.
With love and appreciation for what you shared,
Josh
Well said, Josh. Truth is a razor’s edge, and we must beware erring to the left or to the right! DeYoung’s book addresses these very things. Thanks for your perceptive comments.
Sounds like I need to get started reading it! Thanks, Mark.