As we observe the rift between Paul and Barnabas (Acts 15) the question of Christian fellowship and differing opinions arise. We note that the writer, Luke, states that the contention was "sharp," hence we might conclude that it was no small matter. Barnabas and Paul had worked side by side in their missionary work for some time. For a period, John Mark, a young Christian, traveled with them. But he decided to separate himself from them at Pamphylia. At a later date we see Barnabas insisting that Mark rejoin them in their efforts, but Paul was not having it. Presented here is a difference of opinion seemingly based on personal relationships. Some commentators insist that Barnabas was patient to a fault and wanted to extend a "second chance" to Mark. Some also tend to think that Paul was too stubborn to afford a second opportunity to the young man. Some even contend that nepotism may have played a role in the dispute, inasmuch as Barnabas and Mark were related.
Whatever the case may be, we know that Barnabas continued his mission with John Mark as his co-worker. Paul chose Silas and returned to his ministry. No one involved pronounced condemnation on anyone involved in the rift.
Can Christians disagree even to the point of "sharp contention"? Clearly the answer is "Yes."
But the "Yes" applies only to matters of opinion on which Scripture is silent. On matters of the faith, doctrinal disputation must always be resolved by Scripture.
Many years later, although there is no record of Barnabas and Paul ever meeting again, we see that Paul commends Barnabas to the church and recommends that the church at Colossi receive Mark.
God seems to have allowed the incident to occur so that the work might be expanded in this instance by two mission efforts rather than one.
There has been considerable difference of opinion as to attribution of this motto, but it has been tagged as the "peace maker's" maxim. I have questions about this which I have not completely resolved, What think you?
I grew up in a church in which this motto was on the masthead of the official church paper: “In essentials, unity; in non-essentials, liberty; in all things, charity.”