Scientology thinks it has the “only” way to save mankind.
But I’m pretty sure all religions think they have the “only” way to spiritual salvation.
In the section “141 Things Jehovah Witnesses Can’t Do” on this site- there are several things on that list that indicate people outside the Watchtower are not good people, that they should be feared for some reason. Jehovah Witness children are generally not allowed to play with their public school classmates, Adults Jehovas Witnesses are encouraged Not to socialize with co-workers.
This creates a Fear of the outside world.
Many people in these church communities are 2nd and even 3rd or 4th generation members. They work for fellow church members, their kids attend church affiliated schools, their social lives are usually with other members and they probably attend a lot of church functions. Their entire lives are wrapped up in this culture and their independent thought patterns have changed, some more than others.