It seems that when we as imperfect people start to categorize what sins are more or less offensive to God than others we tend to rank sins which we personally are more partial to as less serious than sins which we are not personally partial to.
I definitely agree with you on this. As believers, most of us have to constantly seek from the Lord discernment of our own motives, our own mild-to-severe treatment of various sins, and even our own selectivity of temptations that we sometimes choose to fall into. This honestly is how we are tempted to be - especially in places where it's easy to wear the badge/label of Christianity without feeling compelled to produce its fruits. God knows I have been guilty of this and continue to repentantly seek Him for strength to obey.
So, while many of us tend to have this partial unstable outlook of big and small sins, that does not negate the fact that correction is needed. Correction is Biblical. Modern-day Christianity and those of us who embrace it would have easily persecuted the apostles Paul, John, Peter, and our Savior Jesus Christ had they walked the earth during our time. To believe that, all we have to do is read what they said about the cross-bearing gospel, read how they behaved during their interactions, read what they said to several people with whom they interacted and further read the Book of Revelation. We would then clearly see that today's interpretation of grace so differs from what Jesus even meant about it, that it's easy to sport the label of "Christian" while living the way the rest of the world lives.
Such statements as "Jesus said don't judge" and "we shouldn't throw stones" that are often spoken among believers (not so much among non-believers) are the very enabling weapons we Christians use against the effectiveness of our own Savior's gospel message. Thus, many on the outside call us hypocrites because of the many sins we overlook - overlooking just so that we don't come across as judgmental.
Part of my point is this: Human nature is to judge anyway. Rarely can we find anywhere a person who's never called anyone too fat, too thin, too weird, politically deceived, socially disfunctional, too lazy, too angry/nice, intellectually inferior (to put it nicely), etc. This is not how we are called to judge others and certainly not in a way to criticize others as if we have no sins to battle with in our own lives. We're to meekly consider our own faults and approach one another with such an attitude - as we proceed to correct. But when we in Christ attempt to fulfill our mission to approach one another with an attitude of correcting to restore (Galatians 6:1-3) - whether it be our spouse or co-worker - or with an attitude of firmer rebuke like standing up to an abuser, somehow we are the ones who should be more careful about being judgmental. As a result, the sins that need correcting among us grow - and grow monstrously because there is no accountability. Ever wonder how so many leaders cause embarrassment to the churches due to pedophilia, materialism, infidelity, embezzlement, drug use, physical violence? Partly, because too people within their circles refuse to correct them. Why? Because we've come to believe the Bible compels us to make such a taboo out of correction.
We are definitely to show grace and consider our own faults. That does not mean throw correction to the wind. I believe this problem is one of the ways Satan presents himself as an angel of light and steals the Word (Which is God's Sword for us) right out of our mouths when we can be effective in helping one another in ways that really matter.
Anyway...I agree with you on quite a bit and see merit for your concerns. But there is much hope in Christ, Who will guide you. Just consider that Jesus actually does see sins in degrees as well as in higher levels of offenses than others. Read John 19:11 as an example and consider that passage at face value without letting any traditionally taught religious propaganda mislead you. No, we are not to take upon ourselves to determine what sins are big or small. It's God's authority alone. Tho, many of us do it anyway - every time we go to the voting polls and vote for the "lesser of two evils"