The biblical view of sin is such that everyone has sinned, not even in the actual action, but even in the thought of a behaviour. Jesus told the people, that whilst it was wrong to commit adultery according to the Law, even to look at a woman with lust is to commit adultery with her in your heart". Same goes with murder. If you look at someone with hate in your heart, it's as if you have murdered them. (Matthew 5:21-22 and Matthew 5:27). Jesus was telling them the eternal truth that it wasn't just the action that was the problem, it is also the hearts attitude.
Infact, the Biblical principle behind this is found in the story of David being chosen ahead of his brothers to be annointed as the new king of Israel to replace Saul. 1 Samuel 16:7 says The Lord does not look at the things man looks at. Man looks at the outward appearance, but the Lord looks at the heart."
So as a Christian, judging someone else without looking first at my own life is called sin. Jesus said "don't look at the speck of sawdust in your brother's eye, and pay no attention to the plank in your own. Luke 6:41
As a Christian the warning is very strong.. no matter how bad the sin is, the action by another person, becareful to condemn them without first judging yourself and seeing you could be guilty of even worse things even without doing anything wrong outwardly. For this reason, Christians believe the ultimate punishment is eternal death for all people, for all have sinned. (Romans 3:23), and without Christ's death, there would be no hope for any of us.
However, what of the punishment for wrongdoing on this earth?
Jesus also said "give to Caeser, that which belongs to Caeser and to God that which belongs to God". (Luke 20:25). Now, whilst this was a specific incident regarding the law of paying taxes, the principle again remains the same. Christians are told to obey the Laws of the land and that means ensuring justice is done if the Law determines punishments for sins.
This however is probably the biggest difference in Muslim Shariyah Law and Western Law. In a Muslim state, the law, and the practises of people are judging from the same perspective. If the Qur'an says this, it's done. In Western Law, there are two types of Law and not all of it is based on Judeo-Christian beliefs as used to be the case with the founding Fathers of most Western countries. Whereas the Scriptures were the basis of what is right and wrong, now adays, non Christian and even atheistic thinking is replacing the scriptures as the foundation of the laws.
Because of the separation of church and state in western countries, just because a Christian believes something because of what the Bible says, does not necessarily mean that the laws of the country will say it is sin as well.
So you get the issue of the Judge in the US who has been stood down for wanting the ten commandments on display in his courtroom. You have different standards of morality accepted. Christians who want to live as the bible teaches face persecution from within their own countries for standing up for truth.
When Christians speak of not all that you see of the west is considered Christian teaching, this is what they are meaning.
Yet, Jesus told His Disciples to expect this more and more as the days of His second coming approach ... Matthew 24 speaks of many of those signs, including the ones talking of how many will turn away from the faith and will betray and hate each other.
Within the churches there is also a discipline structure for sin and within many denominations this is carried out as per the scripture. If someone is seen breaking God's law, they are approached and told about it in private. If they don't react or change their behaviour, then they are spoken to by a group. Paul even speaks of some being put out of the fellowship of believers for their sin. Now remember, this is not the sins worthy of punishment by the Law of the Land, this is for any sin, even those attitude sins we discussed earlier. ..but always in an attitude of remembering.. I too am a sinner, saved only by the grace of God, so there is also an attitude of forgiveness, for we are told to forgive, as we have been forgiven.
I'm sorry for a lack of Bible verses here, but I don't have my Bible with me and am quoting verses by memory. buty, does this answer some of your questions? I'll try again tomorrow if it hasn't.