OK, I will try to be clearer. 'Liberalism' is maybe not the best term, since it connotes a priority of personal liberties, perhaps to the exclusion of centralized power. What I really meant was something more like 'leftism,' and even leftists who 'hate liberals' or whatever would fall under the umbrella.
I see the basic impetus behind leftism roughly as a kind of hyper-rationalism. The leftist has an a priori idea of how the world ought to be, and is outraged that it is not that way. The leftist proposes that the world ought to be changed to be that way, preferably as swiftly and with as little compromise as possible. So leftism is a radicalism in that, insofar as the world is imperfect, it seeks to perfect it, and since it cannot be perfected, it will perpetually be calling for immediate radical change and the dismantling of deep institutions, in favor of new institutions with no historical roots that better match reality as it ought to be.
This means that leftism fundamentally privileges representation over reality in a certain systematic way. I read this cheesy fantasy story that had a great line, where the keeper of the observatory told a visitor that the model of the universe was not perfectly representative of the universe, and when the guest asked, 'so it is imperfect?' the observatory keeper responded 'the universe is imperfect. One day it will be remedied, to fit the observatory.' This is essentially what I see as the guiding impetus of leftism. It is representations that determine reality rather than vice-versa. In this it is fundamentally rationalist in the sense that it believes humanity imposes itself on the world, rather than the world imposing itself on humanity, which is the empiricist bent. The world is as people make it to be, and conforms, and will conform, to the categories constructed for it and placed upon it. This is of course the deep metaphysical source of social constructionism in its various forms, and of the perpetual leftist call to radical political action and revision.
Wherever the leftist sees something that isn't perfect, where the empiricst of conservative impulse is to change oneself to match the world, the leftist impulse is to change the world to match oneself. Rather than meeting a pre-existent standard, like the conservative, the leftist protests that the standard is wrong, and ought to be place elsewhere. Hence the leftist generally does not seek to be beautiful, but to redefine the ugly as beautiful (and even to problematize and hate beauty if it proves too recalcitrant), because he believes, at bottom, that there is no substance to the world other than what he places on it (notice that nihilism of some sort is considered self-apparent to many leftists, or more softly the belief that 'the world has the meaning you give to it'), and so there is a kind of delusion or fantasy of power and control, reflected in the desire for central planning in government and statism generally. This further leads to a conflation between intentions and ends: the leftist thinks that because all reality is malleable to representations, what one needs to do in order to achieve some effect is simply to intend to change the world in a certain way and marshal enough money or power to do so. Hence why the leftist believes that if something is bad, the best thing to do is illegalize it, and so on. There is a kind of naive believe that intentions generate realities. This, in my opinion, is why leftism is grounded on a deep denial of reality, not just as an after-effect (all of us deny unpleasant truths), but as a matter of principle. There is a sense in which the leftist believes that he ultimately cannot be wrong, and where the world bumps against him, the world must move. It also may in turn mean that there are certain things that, while true, cannot or should not be believed, because that would cause one to represent reality in an evil way, making one evil, and so unpleasant truths have systematic reasons to be denied or at least suspended in various forms of doublethink.
This is the reason that the leftist critiques tertiary social phenomena in the media, because they think the media has the power to control thought and behavior rather than vice-versa, and why they put so much emphasis on 'representation' in media and how the media can be used as a tool to change the way people think. This is also why it is utterly obsessed with policing language – it thinks, in a way, you can speak truths into being. Leftism is a top-down ideology, while empiricism and conservatism are, if you like, bottom-up in believing that there are organic features of reality that naturally arise and that one has to accept and conform to if one wants to live. The leftist is in deep denial about the way representations interact with the world, and holds out a secret hope that he can control these representations, and so control all of reality. But this will never work, and so the moral hysteria surrounding trying to perpetually doctor these representations is ongoing and perpetually radical / destructive. Leftism in a way saps adulthood, which is why it makes sense for a university to provide Play-Doh to upset leftist students to calm them after a troubling experience, while doing such a thing is confusing or absurd for conservative students.
All of these, I believe, are features of childhood. The confusion of representation and reality (lack of object permanence), the belief in the malleability of the world to one's desires, the refusal to face unpleasant truths, the insistence that everything ultimately be molded to one's wishes. This creates a desire for childlike narratives and a liking for comic books, superheroes, and so on, along with simplistic moral axes of oppressor-oppressed that create a sort of identity-based template for knowing who is in the wrong when, to emphatically and uncompromisingly support the side that is being hurt by the ones in the wrong. This in turn leads to the basic oppressor/oppressed distinction, which has no fundamental way of being questioned, but only multiplied and complicated by infinitely expanding axes of oppression based on increasingly minutely defined representational categories. And the desire to use this distinction for political gain in enforcing the privilege of one's own representation (and hence reality, since representations determine reality) leads to a weaponization of the notion of oppression, and the glorification of victimhood, weakness, emotional instability, infantilization, and so on. It also leads to the co-opting of natural human emotions, such as grief and anger, into deliberately evoked stratagems employed for specific political reforms. All of this is an endless, destructive spiral that can never be satisfied (since reality will always defeat the representations, while the leftist insists on the opposite), and makes everyone miserable insofar as nothing works insofar as it systematically denies reality.
But this is the behavior of a child – the first thing a child learns to do with its emotions is to artificially invoke them for instant gain, to make its desires a reality. Along with resentment and strategies for revenge against reality when one's desires aren't fulfilled.
––––
OK, scattershot, but that about covers it.