Down through the centuries, and particularly in our time, there has been a seemingly irresistible tendency to sacrifice orthodoxy for the sake of unity. This often involves what may be called the ‘common denominator’ fallacy. If any given group has, say, three people, and two of them believe X, Y, and Z, and one believes only X and Y, what do they all have in common? Obviously, X and Y. But suppose Z is the deity of Christ. Should we, for the sake of the unity of the whold group, reduce our doctrinal basis to only X and Y, and not make a big deal about Z? While this is an admirable approach when it comes to nonessential doctrines, it is fatal when it comes to essential doctrines. Orthodoxy on essentials should never be sacrificed for unity.
This ’common denominator’ fallacy has destroyed orthodoxy in Christian institutions from time immemorial. One cannot count the donomiations, churches and other institutions that have ‘gone liberal’ based on what, on the surface, seemed initially to be an admirable goal–namely to preserve unity. But at what cost! Real orthodoxy on essential doctrines should not be sacrificed on the altar of alleged unity.
~Conviction Without Compromise by Norman Geisler and Ron Rhodes, pp. 353-354