How should I regard Christians who "follow not with us?" a young believer may ask.
Well, how would that Great-Heart, the Apostle Paul, have regarded them? Are they not children of God? Hearts may agree although heads differ. God sees grace—where we see none. If you think that these people have less light than you, their need is a claim upon your help; and, believe it or not, they can teach you something! Be on your guard against viewing them with suspicion or contempt. You are made of exactly the same flesh and blood as they are, and the same grace is at work in them as in you. God loves persons rather than places.
You may not find every believer very approachable; but try to cultivate spiritual fellowship with all God's people by dwelling upon the foundational things that all true Christians hold in common. In this way you will help to "keep the unity of the Spirit in the bond of peace." Be a living link of fellowship between believers. Sympathy is better than criticism.
Do not take the world's side against God's people.
Each group or school of thought has its own emphasis, and sometimes its own phraseology.
Do not attach too much importance to religious phraseology; the same truth can be expressed in different ways. We should learn to welcome all the truth, through whatever channel it may come to us.
N.B. The above emphasizes one aspect of the Truth which some extremists need to take to heart. There is a happy medium between refusing to walk with "those in error," and declining to have fellowship with any who fail to pronounce all our shibboleths. —Arthur Pink