I don't think there is such a thing as a true religion or that God is an exclusive experience to theists or even only to those who believe in God.
My parents were not particularly religious. They gave us kids a great Christmas and Easter once or twice when I was in elementary school but never observed Passover or celebrated Chanukah. We walked a few times into a church, but was only briefly told about our connection to Israel when I was 16 (we did eat kosher though, but I think it was only out of habit and familiarity.) And that was it--end of my sporadic religious upbringing by age 9.
The only time I was exposed to the idea that there was a "true feligion" or that one needed to find "the Truth" regarding life was when I was introduced to the Jehovah's Witnesses by my aunt who took over raising me as a boy by age 17. I never heard of such a "one truth" concept from anyone else I knew before or hear it from anyone in my circles today (except from some Mormons who came to my door a few times and a few Catholic friends who were influenced by growing up in the Bible belt of the U.S.).
From my experience as a regular pioneer when I was a JW and comparing it to my 20 years of life since, very few religious people believe theirs is the true religion or that only one true religion or one truth exists. It is an earmark of NRMs, some Fundamentalist Christian movements, a few disconnected others from just about any other walk of life maybe, but I can't say from my personal experience that it is a common trait to anyone else, religious or otherwise.
However after watching several documentaries on life in North Korea, reading about the way people there view their rulers (and how the rulers have practically made deities of themselves), I think the idea of "having the only truth" or being a member of the "best" or putting all of one's figurative eggs in one "basket" makes certain religious movements and their adherents the zombie-like Kool-Aid drinkers that they are. The formula, as North Korea demonstrates, is not exclusive to any religious experience.
As the secular North Korean paradigm demonstrates, you can take religion totally out of the picture and still get the same type of propaganda-drunk followers. Sometimes people are forced to believe these things, other times they are free to do so, but it is naive to think that religion itself is a necessary ingredient if you want to make mindless sheep.
As a hypothesis I put forward the possibility that it's the idea that there is only one way, one "truth" that causes people to act as they do in these situations. Whether it be the Watchtower, New Age crytals, the secular regime of a dictator that outlaws religion, or a group that promotes loving Jesus but hating everyone else, the common denominator is that these people convince themselves that only their view is correct and that of others isn't.
It seems to be that it is the "one-truth-only, and-I-have-it-but-you-don't" concept that may be the real poison, and not religion or any particular secular philosophy that causes this.