Thank you everyone for your ideas. David_Jay, yes I'm looking for that word that describes the "separatism" they practice so the dehumanizing consequences of "disfellowshipping" have some context to an outsider. Tal, "isolationism" sounds good but the more I think about it perhaps I should use more words to explain what's happening. Joe, perhaps "reclusive"...
I'm looking to explain how important my spouse is to me especially in light of the fact that my social network was severed when I left the Jehovah's Witnesses. This is the sentence so far: (any suggested improvements welcome, and thank you!)
Since Jehovah's Witnesses strongly discourage social contact with outsiders shunning has a more detrimental effect on individuals than may be realized by those not familiar with their practices. The [insular/clannish/isolationist/reclusive] nature of the group amplifies the significance of relationships formed after excommunication as these form the basis of an entirely new social network.