Consequences of "In Group" and "Out Grouping"

I'm always interested in what happens with in/out grouping amongst various groups. Karen Armstrong offers the following that caught my attention yesterday. The quote is lengthy but for me, it was important to put this in its proper context.

"A tightly knit and isolated community however, can develop an exclusivity that ostracizes others. In Asia Minor a number of Jewish-Christian communities, who traced their origins to the ministry of Jesus’s apostle, John, had developed a different view of Jesus. Paul and the Synoptics had never regarded Jesus as God; the very idea would have horrified Paul who, before his conversion, had been an exceptionally punctilious Pharisee. They all used the term “Son of God”  in the conventional Jewish sense: Jesus had been an ordinary human being  commissioned by God with a special task. Even in his exalted state, there was, for Paul, always a clear distinction between Jesus kyrios Christos  and God, his Father. The author of the Fourth Gospel, however, depicted Jesus as a cosmic being, God’s eternal “Word” (logos) who had existed with God before the beginning of time. This high Christology seems to have separated this group from other Jewish-Christian communities. Their writings were composed for an “in group” with a private symbolism that was incomprehensible to outsiders. In the Fourth Gospel, Jesus frequently baffles his audience by his enigmatic remarks. For these so called Johannine Christians, having the correct view of Jesus seemed more important than working for the coming of the kingdom. They too had an ethic of love, but it was reserved only for loyal members of the group; they turned their backs on “the world” condemning defectors as “anti-Christs” and “children of the devil.” Spurned and misunderstood, they had developed a dualistic vision of a world polarized into light and darkness, good and evil, life and death. Their most extreme scripture was the book of Revelation, probably written while the Jews of Palestine were fighting a desperate war against the Roman Empire.  

The author, John of Patmos, was convinced that the days of the Beast, the evil empire, were numbered. Jesus was about to return, ride into battle, slay the Beast, fling him into a pit of fire, and establish his kingdom for a thousand years. Paul had taught his converts that Jesus, the victim of imperial violence, had achieved a spiritual and cosmic victory over sin and death. John, however, depicted Jesus, who had taught his followers not to retaliate violently, as a ruthless warrior who would defeat Rome with massive slaughter and bloodshed. Revelation was admitted to the Christian canon only with great difficulty, but it would be scanned eagerly in times of social unrest when people were yearning for a more just and equitable world. "

– Fields of Blood by Karen Armstrong – Jesus Not of This World? – pages 144-145 - emphasis mine.