Narksis,
I am not defending the practice of df'ng among Jehovah's Witnesses as i believe it is one which should cease and is destructive and counter-productive, not too mention unscriptural.
as for your question, the explanation essentially has to do with the degree to which adherence to a set of items is tolerated or necessary for the group.
to illustrate:
The Club of Farsandia holds that members in good standing must believe without dispute or denial (and that is the key "without dispute or denial")
Belief A, Belief B, and Belief C. and must perform Ritual 1, Ritual 2, and Ritual 3
these are fundamental requirements of membership. anyone who doesn't state they believe them or gives evidence in not believing them can't be in the Club.
so far so good i think. Most people would agree that the above is not outlandish and it is ok for the Club to establish these basic requirements of membership. (That is my fundamental premise in my post.)
Now, however, among some Farsandians, there are the Beliefs D and Beliefs E, and a Ritual 4.
The issues raised by my post address the situations where these non-essential beliefs may or may not be tolerated.
If the Farsandians are a tolerant group they may consider Farsandians who also Belief D and E and practice Ritual 4 to be approved members of the Club even if they disagree with those items or even if they are not "official" or requirements for membership. On the other hand, if they are not tolerant, they might try to exclude the Farsandians who hold the extra beliefs or who practice the extra ritual.
My personal opinion is that I think it is better when a group is more tolerant than not but of course this would depend on the specifics of the differences. If for example Belief D happened to completely contradict Belief A then it could not or should not be tolerated by the Club and the person could not, by definition, be a member.
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I wasn't going to expand but maybe it is necessary.
So my concerns regarding JWs is that DF'ng is used to silence criticism about what are essentially (in reality) non-essential or completely wrong beliefs and practices. Blood for example. Or DFng Bill Bowen for raising concerns about policies, practices and doctrines that result in potential harm to others.
DF'ng because a person doesn't hold to a belief in God, Jesus, an accepted minimum standard of moral conduct, etc., I have no problem with as I would view those things as essential to the definition of group membership.