A normal religious organization would not have any trouble with you
moving to another similar organization as long as you stayed in that
same religion. Because it is the belief system that matters, not
membership in an organization. For example if you were a Christian then
you could move from one church to another and still be a Christian.
However cult leaders will tell you can only be “saved” (or can only
be successful) in their organization alone. No other organization has
the truth, all others miss the mark. So it is not the belief system that
decides your future, but it the belief system AND your membership with
that particular group.
The cult leaders need to make you believe that there is no where else
you can go and still be saved, and if you ever leave the “one true
church” then you are going to hell. This is a fear based control
mechanism designed to keep you in the cult. It also gives the cult
leaders tremendous power over you. If you really believe that leaving
the group equals leaving God (or means you are leaving your only chance
to succeed in life), then you will obey the cult leaders even when you
disagree with them instead of risking being kicked out of the group.
Exclusivism is used as a threat, it controls your behavior through fear.
Be very suspicious of any group that claims to be better than all the
others. A religious group may say that other groups following the same
religion are OK, but they are the ones who have a better grasp of the
truth and they are superior to the rest. This is often just a subtle
version of exclusivism.
This is one of the practices that cults are often very deceptive about.
For example, first off they may give you the impression that they think
you are a true Christian, Buddhist or Muslim and it’s not until later
that their true position is revealed.