One thing that I have observed is that for a leftist, human nature is truly a puzzling affair. After all for him, all is relative. All aspects of human society, culture, morals are but a cage some other powerful humans have erected over us. It's like living in the Matrix, all these silly sheeple blindly following what THEY pretend is normal and they don't even question it!
No! Impossible! These fellow humanoids are brainwashed! They are not acting in their best interest, but according to the rules of the framework that benefits their masters!
Everyone needs a framework to orient themselves in life. The difference being that, people with a higher degree of trait Openness (let's lump the "Leftists" along with them, whatever) are more driven to explore different possibilities of what their life might look like.
And they often feel threatened by the prejudice that less open people often harbor for people exhibiting behaviors that deviate from the norm.
This is an experience of threat that's less talked about, as opposed to the threat by the "other" that conservative people experience.
Here's another cage to consider: language. We are limited in what we can think by the language we use. There are infinite things expressible using language, but still, doesn't it seem like there's ''stuff'' out there that can not be expressed using language, not only at a personal level (limited by the amount of knowledge obtainable in a lifetime) but also at the global, or even, universal level. Even if you add emotions, feelings etc. in the mix, there might still be stuff that can not be perceived by our minds at a collective level. What would you feel about this?