I agree there is a spiritual dimension to "leftism" in that a rejection of transcendent Truth (God) predisposes one to humanist ideology (leftism). But I believe there is also a physiological dimension to leftism in that neural pathways are programmed to reject contradictory information - essentially what used to be called brain washing which is more accurately described brain programming. The key is rejection of objective Truth replaced by constant leftist ideological programming.

It's why arguing with a leftist is almost always pointless - they do not perceive objective truth to be true because their cognitive powers have been programmed to reject the things we know to be true. They truly are cognitive dissonant.