Every organization requires rules in support of order, discipline, and efficiency-and the church is no different. We, too, have rules that aid in the organization and operation of the church. (There is always some measure of institutionalization required in the church.) In addition, we have established other rules that aid in the understanding and practice of the faith such as creeds, confessions, statements of faith, doctrinal statements, and so on. These are helpful guides to what we believe. What they don't say is what we don't believe. These conclusions we may draw by implication.
For example, your local church, tradition, or denomination may subscribe to adult baptism or "believer's baptism" and this belief may be included in your doctrinal statements. Then you encounter another Christian who subscribes to infant baptism (paedobaptism) and you may assume by implication that their belief is wrong (because it differs from your institutional convictions) and thereby conclude it must be a false interpretation of biblical faith.
Christians have throughout the centuries-and most especially following the Protestant Reformation-arrived at very different understandings about a multitude of issues related to the teaching and practice of the Christian faith. Unfortunately, we tend to form enclaves around these doctrinal understandings, which are eventually institutionalized into denominations, thereby distinguishing us from other Christians. The result is sectarianism, which can create divisions within the body.
No longer is there such a thing as "mere Christianity" to borrow C. S. Lewis's phrase, but Catholic-Christianity, Protestant-Christianity, Orthodox-Christianity-not to mention the countless Protestant denominations and nondenominational representations of Christianity. Universal fellowship centered on the person and work of Jesus Christ is exchanged for tribal commitments to traditions and various nonessential views.
This is not to say that we shouldn't have deeply held doctrinal and theological convictions, merely that we should recognize that the Scriptures often leave room for the many varied interpretations of Christian practice. As the late Dr. Francis Schaeffer pointed out, the Bible is true truth-sufficient for salvation-but not exhaustive truth. It's completely true about everything to which it speaks, but it doesn't speak about everything there is to know (see 1 Corinthians 13:12). Given this condition, which the Lord has determined, it becomes dangerous to speculate through implication on those things that are not essential to salvation and elevate them to essential beliefs that divide.
If we take seriously the Lord's request of the Father that we "may be brought to complete unity" (John 17:23) then we would be wise to listen to and fellowship with one another in a spirit of love and charity; for according to Christ, this is how the world will believe that the Father has sent the Son (see John 17:21).