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The whole point of the Romans 14 passage is that believers in Christ are bound together in Him. We will have our differences of opinions, we will disagree with them on issues. We will believe that they’re wrong and we’re right.
But we’re to remember the grace by which we were saved, and extend that grace to them. We are to realize that they are living their life out before their maker, and unless they are in a sin which is spelled out in the Bible, we’re to grant them the ability to live out their Christian liberty.
That being the case, how do we settle problems and differences among us? With dialog between the two people—the one that has offended and the one that has been offended.
The Bible is very clear—regardless of whether you are the offended or the one offending, you’re to go to the other believer and work out the differences. If there’s sin involved, it may be necessary to bring along another believer—or the church—to help settle the problem.
Unity in the body of Christ was something that Jesus prayed for in John 17. This doesn’t mean that we’ll always agree on everything, but we should strive to live peaceably with all men—especially our brothers and sisters in the faith. We should treat them better.
The verse that says “they will know we are Christians by our love” isn’t talking about our love for the godless or the poor, it’s talking about our love for other believer.
So, my question is, are you “right” with the other believers with whom you associate? Is there a cavern there, a place where you’re either on the giving or receiving end of the silent treatment?
If so, then you need to go to that brother and get the matter righted.
