There are many ways to respond to a story such as this, with encouragement, sympathy, logic but in the end I think happiness is best. Not all belief systems nor all people are dangerous and destructive but many people who would not be dangerous become so when they fall prey to legacies of ancient hatreds.
Living with someone, particularly as a child with their parent, captured by these beliefs makes it nearly impossible to avoid pathological consequences. While people are amazingly resilient the damage done usually takes years to overcome yet we have no way to prevent this or to protect children from it.
But, in my experience, it does make you stronger and healthier if you survive. And most people survive. That seems cruel to accept but there is no real choice.
The real damage is when the child cannot escape the trap of pathological beliefs and repeats them for another generation. That, of course, is the goal of those who are part of these vestiges of a past mythic age.
The reason that this pockets of older belief systems survive and become diseased is another topic. But they do survive and draw people in certain conditions in and those people are only partially touched by the pathology of these systems. Unfortunately we can’t control or even say when and in what ways that will drive them to hurt those around them.
It seems, though, that you have survived this well and can move on.