"What frightened the parent was the community had embraced and accepted her son in a way he had never experienced in his entire life. Those are very deep psychological strings being pulled and that seduction is wrapped in racist ideology. This child could probably rationalize believing any ideology in exchange for that acceptance and belonging ..."
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This same thing that happens with gangs and other extremist groups also happens with religious cults, e.g., evangelical Christians.
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The convert then cuts off their own family, and replaces it with their "church family".
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The religious brain-washing is total.  Any family member who disagrees with church dogma is instantly excluded from any further contact, for life.
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They never ask themselves what kind of religion teaches that you should hate your own family.
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The effect on the family members who are then rejected is devastating - not unlike the effect of having a parent with dementia, who no longer recognizes their children.