Romans 14:4 Who are you to judge the servant of another? Before his own master he stands [approved] or falls [out of favor]. And he [who serves the Master—the Lord] will stand, for the Lord is able to make him stand. AMP
Let me make this as clear as possible from the start, I am not talking about the doctrines of pastors and teachers. This is only about personal doctrine of individuals with whom you are in fellowship with or are developing relationships. A whole different set of standards exist for pastors and teachers.
There will be times when error is noted with group settings, large and small. As we begin to develop relationship there is going to be gaps in experience and varied doctrinal histories. More often than not we find the lingering effects of culture, parental influence and diverse teachings. It is best we look at these diversities as universal. They see the same in you, diversity. How we handle these diversities determines if the bonds of fellowship are strengthened or weakened.
Ephesians 4:3 Endeavouring to keep the unity of the Spirit in the bond of peace.
If we take unity into first account, that the relationships must be formed and bonds developed first. Then as we continue in fellowship, the diversities can be approached later with the calm appeal to a friend. It may be that over time, as we get to know one another more intimately, that those diversities we first noted are not as important as seen at first.
Which leaves us with the issue of handling true error. Do you serve the Lord, is He your Master? Then your response should be to act in accordance with the Lord’s instructions. If you take issue with what one person says in a group setting, do not confront them in the group setting.
Matthew 18:15b tell him his fault between thee and him alone:
While Matthew 18:15 is about an affront, the same principle applies. Open confrontation within a group setting breeds distrust and discord. We should not be that person.
Proverbs 6:14 Frowardness is in his heart, he deviseth mischief continually; he soweth discord.