I believe they face the same terror that we did, all who have moved on from their teachings.
Their whole lives revolve around the ritual of meetings, preaching and hangin' out with people who believe the same.
To revoke their beliefs is to face death of the ego, basically a form of madness, as they would need to reform their whole persona.
It's fear of admitting their lives have been in vain (and change) that creates their blindness just like most thinking witnesses.