The Holy Spirit has not only instructed us clearly on the marks of a true church and how to recognize false teachers; the Lord also requires believers to adopt a Biblical attitude toward false teachers and conduct ourselves accordingly.
The New Testament states that once we have identified false teachers by the standard of Scripture, they are first of all to be commanded to desist. They are to be shunned, so that they might become ashamed and repent; but in the beginning they are still to be treated as brethren and not as enemies (Matthew 18:15, 2 Thessalonians 3:14-15, 1 Timothy 1:3).
But if men persist in false doctrine, after the first and second admonition (not the tenth or twentieth) they are to be rejected (Matthew 18:15-17, Titus 3:10). The people of God are commanded to note them and avoid them (Romans 16:17). They are to withdraw themselves from them, certainly not make them leaders of the church (2 Thessalonians 3:6, 1 Timothy 5:5). They are not to offer them even a single word of encouragement or support, and not even meet with them privately, because doing even those seemingly harmless things is to share in their evil deeds (2 John 10-11). Those who persist in error and do not submit to correction are to be treated as lost sinners who are in need of the Gospel themselves, no matter what titles they may hold in the church or in academia (Matthew 18:17).
Dealing Biblical With False Teachers is Never Easy
Adopting a Biblical attitude toward false teachers and dealing with them accordingly is never the easy or convenient thing to do. But Scripture is clear and unequivocal. The Holy Spirit leaves no room for doubt as to the Biblical course.
Following that course will have a cost. Those who stand for the truth will suffer the loss of friends. Truth and error may even divide families, much less congregations, presbyteries, or denominations, but Jesus told us this would be the case:
Therefore whoever confesses Me before men, him I will also confess before My Father who is in Heaven. But whoever denies Me before men, him I will also deny before My Father who is in Heaven. Do not think that I came to bring peace on Earth. I did not come to bring peace but a sword. For I have come to "set a man against his father, a daughter against her mother, and a daughter-in-law against her mother-in-law"; and "a man's enemies will be those of his own household." He who loves father or mother more than Me is not worthy of Me. And he who loves son or daughter more than Me is not worthy of Me. And he who does not take his cross and follow after Me is not worthy of Me. He who finds his life will lose it, and he who loses his life for My sake will find it [Matthew 10:32-39].
We may submit to God's commandments or not, but they are still the truth, and obedience is the only acceptable course, even if it is a difficult one.