I've been working on a different theory: These people are, almost uniformly, aetheists.
Having turned their backs on God, they experience a terrible, deep-seated emptiness in their lives, and this socialist/materialist/elitist/hedonist/narcissist culture BECOMES their religion.
I.e. it is not that their beliefs systems have snapped shut like a box, but that "socialism" [or materialism, or elitism, or hedonism, or narcissism, or whatever you want to call it] is precisely their belief system, and they are committed to it with the same sort of religious fervor that the jihadists are committed to the Koran [and its unequivocal commandments to murder us, the infidels].
"Religious" peoples [read: classical "Protestants" - I don't know that I understand "Judaism" or "Catholicism" well enough to comment on them, although I fear that I do] don't suffer from this sort of investment in the here and now - rather, their hopes and dreams are invested in the hereafter, so if their candidate fails to become Ward Boss [and hence can't deliver the goods], then it's no big deal.
They just shrug their shoulders and get on with their lives.
I appreciate your observations. I would agree that spiritual deadness is likely associated with the existential emptiness you identify, and leaves the unbeliever vulnerable.
I don't know that all these people are atheists, they might be, but the way I would approach it is to allow that people can reach this endpoint by diverse routes.
Once there, the common element is being totally closed to any message which is discrepant from an exceedingly narrow and intensely held attitude. Questions of true and false, accurate and distorted, pale to insignificance.
For these dead-end true believers, the sacrifice of truth is a small price to pay for the sake of the cause.
Their ego is so deeply involved in their view of the world, that any input which raises a challenge to it is taken as a personal assault. Hence the hostility and rage.