Can you give me a scripture that states that Christians (or Bible believers) are 'dutifully bound to judge behavior'?
Moral judgments are essential and the Holy Bible is filled with them.
It is clearly incumbent upon us to judge. There is a clear distinction between judging an action, and the motives behind such actions. We can clearly see the act, but it is difficult to understand what motivated it. In other words, we can judge the act, but not the soul, for it is in the soul that motives lie---the latter is for God to judge.
1Cor 5: 1-13---------St.Paul lays down some seemingly harsh measures for dealing with those who are sinning. He tells them not to associate with or shun those who are immoral, covetous, an idolater, an abusive person, a drunkard or a thief.
"But now I have written to you, not to keep company, if any man that is named a brother, be a fornicator, or covetous, or a server of idols, or a railer, or a drunkard, or an extortioner: with such a one , not so much as to eat. For what have I to do to judge them that are without? Do not you judge them that are within? For them that are without, God will judge. Put away the evil one from yourselves."
Christ made a similiar statement about the recalcitrant sinner in St.Matt. 18. If these unrepentant people are left with no one to chastise them they could lead others into sin or promote an unhealthy tolerance for evil conduct.
See 1 Cor. 6 for what St.Paul means by an immoral person, Do not deceive yourselves: no fornicators, idolaters, adulterers, sexual perverts, theives, misers, drunkards, slanderers or robbers will inherit God's Kingdom. Gal. 5 he condemns lewd conduct, impurity, licentiousness, idolatry, orgies, etc. warning those who do such things will not inherit the Kingdom of God.
6:1-5--------Dare any of you, having a matter against another, go to be judged before the unjust , and not before the saints? Know you not that the Saints shall judge this world? And if the world shall be judged by you, are you unworthy to judge the smallest matters? Know you not that we shall judge angels? how much more things of this world? If therefore you have judgments of things pertaining to this world, set them to judge, who are the most despised in the church. I speak to your shame. Is it so that there is none among you any one wise man that is able to judge between his brethren?
2St.John 10-11-------If any man come to you and bring not this doctrine, receive him not into your house nor say to him, God speed you. For he that saith unto him, God speed you, communicateth with his wicked works.
Leviticus 19:15------Thou shalt not do that which is unjust, nor judge unjustly. Shew neither partiality to the weak nor deference to the mighty. But judge thy neighbor according to justice.
19:17-------Thou shalt not hate thy brother in thy heart, but reprove him openly, lest thou incur sin through him.
St.Luke 12:57-59-----And why even of yourselves, do you not judge that which is just? And when thou goest with thy adversary to the prince, whilst thou art in the way, endeavor to be delivered from him: lest perhaps he draw thee to the judge, and the judge deliver thee to the exacter, and the exacter cast thee into prison. I say to thee, thou shalt not go out thence, until thou pay the very last mite.
St.John 7:24 in which we learn there is no doubt that we are to judge one another's words, actions and deeds with the provision we that we judging rightly, or with justice or justly.
The general guiding principle is found in St.Matt 7:12 which is true even for even those who don't believe in God or the non-religious "whatever you wish men should do to you, you also do to them."
With regard to homosexuality, we often hear "Don't be judgmental", but this is nonsense becasue the act is clearly to be condemned. We can and must judge the act saying it is sinful and against God's law. We can and must judge justly when it comes to homosexuality especially when taking steps to protect our children from the influence of such individuals.