" 15–20% of Americans are in a cult, so it seems reasonable to assume this isn’t something to be taken lightly."

Sociologists generally agree that the tipping point for adaption into mainstream for social/political concepts is as low as 15% of the population. So, yes, this is something to be very concerned with. However, it is difficult to isolate such belief into their own niche without acknowledging that the government and institutions of our society are no longer in the control of the people or working for their benefit.

Once people become disillusioned with the very fabric of their society as a force for good in their lives, especially among a group predisposed to magical thinking and shunning critical/scientific thought, the sky is the limit for those beliefs.