If you don't currently own "Conjectures of a Guilty Bystander" by Thomas Merton, you should. In fact, you should leave this page and immediately go to Amazon.com and buy it for yourself. I have read this book several times, and keep it around as a trusty companion. Merton was a modern mystic and his writings make him a sort of spiritual director for me as I seek to see what a mystic Christianity looks like in a world growing deeper and deeper into cynicism.
In one of his more convicting sections of this book, Merton poses the question as to how Christians can come to be so judgmental. This is the seminal question I have for modern Christianity as well, as it seems to be a constant complaint of non-believers. What is wrong with us? How is it possible for us to miss the point so horribly? Who are we, recipients of undeserved Grace, to call someone else a "sinner?"
In simpler terms, if a non-believer finds you judgmental, they are finding you unChristian. If you at any point think of yourself as better, more loved by God, or more worthy of eternal communion with the Creator, then you are lost.
You can't be convinced of Christ's sacrifice and free gift of a love you don't deserve if you act like you deserve it.
Grace is opposed to your judgement, it is against the idea we have of hierarchy of sin, and it transcends our theological nonsense about who is "in" or "out" of the Heaven we hope to escape to. Who is this grace for? Everyone. The worst offenders. The scum of the earth. The people we don't want to be friends with because they are "living in sin."
The one place all people are truly equal is at the bottom of an ocean of undeserved Grace.
Coming to understand Grace, the idea Jesus thought we were worth dying for even though we are decidedly not, is the hardest part of the Christian journey. Coming to understand everyone is equal to us in unworthiness--yet God loves all of us more than we can imagine, is the first step toward a complete and holistic understanding of our identity in Christ. We are all in need of reminding of the words of Paul in 1 Timothy 1:15, "Christ came to earth to save sinners, of whom I am foremost." At the same time, we must also remind ourselves of Christ's love for us, and his desire to call us brothers and sisters. The dichotomy of the Christian life is found right there. We are guilty of disrupting the Peace (shalom) God had planned for us and the world, yet God's love for us won't allow for that to be the last word. He makes a way for us to experience union with Christ, to be seen by God as in Christ, and to be with Him forever--starting right now.