I realized that my comment was getting crazy long so I figured I better create a separate post.
Regarding the behavior of the church in the area of obvious sins, judging others, defining holiness, etc.
I think what it usually comes down to is well intentioned people trying to "help" others not "fall into" sinful patterns or behaviors that could lead to sin. For example, the Bible tells us that drunkenness is sin but does not say that drinking alcohol in moderation is sin. We are told that our bodies are a temple of the Holy Spirit but not what that means in terms of our diet and other habits related to our physical form. So people who desire to guide the saints in holiness will create fences around the "laws" that are explicit in scripture to protect them from committing those sins. (e.g. to keep you from getting drunk, we will tell you to avoid all forms of alcohol or to keep you from harming your body, we will tell you NEVER to smoke and that smoking is a sin)
My guess is that this is a root that has been growing in the church since the beginning when Christianity was made up of religious Jews. In fact, the apostles and early church had a few incidences where they had to wrestle with laws and defining sin and behaviors of holiness (the Jerusalem counsel is one that is probably the most memorable for my brothers in Christ *wink*)
Much of the Jewish law had to do with the yolk the people put themselves under (and actually still does today). The yolk was the specific teachings of a particular rabbi. He would interpret the law (the 413 spelled out in the Torah) and determine the specifics and you would place yourself under those interpretations and follow them. For example, the Law says to keep the Sabbath but gives very little in the way of specifics. So what does it mean to keep the Sabbath holy? How do we define work? How do we define rest? So each Rabbi would define those things and tell his followers and they would "yolk themselves" to those laws.
...and what did Jesus say? His yolk is light.
Christian leaders, pastors, elders, denominational leaders etc. all end up referring back to a few things in particular when they prescribe behaviors or try to guide choices 1. not causing a brother to stumble 2. becoming more Christ like, more holy and/or more sanctified depending on their choice of wording and 3. avoiding the appearance of evil.
1. this is good to keep in mind but not a reason in and of itself to avoid a behavior that isn't explicitly forbidden, esp. since that verse is horribly proof-texted to serve specific people's agendas. I will say that choosing the "high ground" or the "narrow gate" (in Bible terms) often means giving up freedoms or perceived rights for the benefit of others or to the glory of God. We do need to be discerning and listen to the Spirit to make sure we are sensitive to that and willing to make those sacrifices....but not because we're afraid to "sin". We do it for love of God and for his Glory and for the love of others.
2. another good thing - yes, we want to become more Christ like. But there are no prescriptions in the teachings of Jesus about the superficial things that Christians usually focus on. Jesus called us to much higher levels of holiness - such as giving up your possessions, caring for the poor widow and orphan, bringing healing and reconciliation to people, loving the unlovable, touching the untouchable, giving people hope, laying down our lives, etc...and Jesus usually did those things while "mingling" with the "worst sinners" of his day and doing the very things that we are told not to do because of numbers 1 and 3 above.
3. avoiding the appearance of evil all comes down to personal and cultural perception and is subject to interpretation. Does avoiding rated R movies actually help you in avoiding the appearance of evil in our current culture? What about not cussing or using nice little "Flandersesque" language? not in our town - but maybe it does somewhere else. It's something we should be conscious of but not obsess over or create a burden for others by giving them a yolk that is heavier than Jesus'
What's interesting about this issue is that it is just as strongly commanded not to burden others with laws that weigh them down and are of man and not God than it is commanded to live a holy life.
Finally, I think it's always important to keep in mind that we can only be responsible for ourselves and judge ourselves. We can share our experiences and encourage others to chase after God, but ultimately, we cannot create laws for other people's lives. I have found in all my "leadership" experience and relationships with other Christians that loving people, encouraging them, taking a genuine interest in their lives and showing them who they are in Christ is the best way for people to grow. Pointing out sin (except in specific cases of destructive patterns of behavior) rarely actually accomplishes much of anything lasting.