It sounds like the beginning of a list, but actually, it is the second point of a two-point list which began in verse 10. In Matthew 22.
Now there are offences and wrong doing and wrong views and Christian teachers who seem to believe the fundamentals of the faith and seem in their way to sincerely teach them, and yet they make, what seems to us according to our degree of light, very great mistakes which mislead people. What do we do? Write them off, assume them to be tools of Satan, evil, simply and only to be rejected? We have to take care because we are under the law of love. So wrongs have to be righted, and if it is the public teacher who is misleading people, well yes, we do have to say that is not right for this reason and try to correct. Shall we go further? Shall we say, He is a scoundrel, he is unconverted, he is terrible, he is awful? I am talking about somebody who holds to the truth, he seems to sincerely proclaim the Gospel. Well the errors may be such that we cannot work with him, we cannot go right alongside him. But we dare not condemn him. To his own master, he must stand or fall. God must be his judge. We can make it clear what is wrong and what is right, but beyond that we cannot go. We can decline to work with but we cannot enter into judgement. We can only pray for change, transformation, for improvement and so on. There are boundaries even in the correction of wrong.