Current conservative and libertarian repudiation of postmodernism is unwarranted and arrogant. Actually also ignorant. The term "postmodernism" has been in circulation since around 1980 and associated with Lyotard's proclamation of distrust toward "grand narratives." Yet the distrust has been in fact brewing for more than 200 years.
Since the time of Enlightenment a new direction of thought has been initiated - a direction dedicated to serving the question about how it is that we know rather than discovering and explaining what we know. This was the Kantian revolution, which Kant himself called Copernican, that put all knowledge in question and created the foundations of the endeavor called science. Yet at the same time Hegel dedicated his work and talents of persuasion to modernizing the older great questions of philosophy and gave rise to Marxist thought.
These two streams of post-Enlightenment philosophical thought have been with us for the last 200 years and both are in some way embedded in what is now called the postmodern philosophy. American political ideology seems disdainful of both since it is mostly founded on thought just prior to the 1800s and has been enormously successful in history. Marxism and Hegelianism maintain that we are determined by the circumstances of history and social situation and our project ought to be to understand and possibly influence those conditions. The Kantian lineage emphasizes epistemology, or the science of getting to know and value things, which studies various aspects of human experience.
After 1900 Marxism has been tainted by political regimes that embraced its versions to enslave millions. In its more benign editions Marxists pursued adaptation to existing political systems (e.g. the Frankfurt school) - seen by their foes as relativism. Yet also in 1900s a new impulse was given to the Kantian flank by Husserl who initiated a new program of phenomenology while Freud started talking about the unconscious. Phenomenology is the rightful descendant of the Kantian revolution and the progenitor of existentialism with Heidegger and Sartre being its main exponents. While these two existentialist standard bearers professed variously Fascism and Marxism the fact remains that their work was mostly dedicated to the Husserlian program of study of the depths of human experience - wherever that study took them. Quite often, and absurdly so, it led many to Marxism, through its attractive call to action to enact the ideal, - which is these individuals' unconscionable error.
To our contemporary classical American liberal, libertarian or conservative, postmodernism's main faults are its denial of "objective reality" and its presumed embrace of relativism. The examples of that are the tenets of gender theory that seem to contradict firm scientific facts of microbiology and physiology and the dead-ends of identity politics where individuals are captives of their social, racial and infinite other intersecting situations. Yet the same liberals and conservatives would be hard pressed to justify human rights or the idea of equality before the law by recourse to science or objective reality. They would have to reach back to Locke for natural law or to God. Here postmodernism with its emphasis on the subjective is really a strong ally of classical liberalism.
Let's play postmodernists now. Objective reality is only objective as far as the subjective constitutes it as such. Hannah Arendt so explains Husserl's discovery: "just as every subjective act has its intentional object, so every appearing object has its intentional subject." Objectivity is a social and subjective convention while reality is not. But we do not have access to reality other than mediated by social constructs such as language. I could quote Lacan or Derrida here. The exceptional situations where we access raw reality is sex, death as well as intense pleasure and suffering. Outside of those situations we filter reality into facts that can become objective so that we can construct knowledge as well as values. Nature, or reality, does not care about our facts, be they objective or not. Nature does not care how we interpret her gifts and torments. Nature does not care about our knowledge of reality.
How do we know that? Well, postmodernism is still working on the question.
The capacity to create and discern objects in uncreated reality is a unique faculty of the subjective. The subjective faculty demands a standing as a human right and the full protection of the law. Perhaps the subjective is what is unconsciously talked about in the US Declaration of Independence as the "pursuit of happiness"?
Postmodernism is largely concerned with the structure of the subjective human experience which is more "absolute", more commanding, than objective reality. That subjective experience also demands protection as a human right, broadly expressing a call to sexual freedom, - manifested currently loudly by the Left through identitarian LGBTQ demands.
The classical liberal or conservative decrying and ridiculing postmodernism should ponder the idea that perhaps just because certain notions are socially or subjectively constructed rather than naturally arising it is not easy or painless to shift them for an individual or for a population.
Let us take up two concepts, variously dear to and hated by, both conservatives and leftists.
Gender is a social construct. It is a social presentation of a subjective sexual desire. That sexual desire has a source in reality - but, as subjective beings, we don't know as a matter of experience while actual biological science has a pretty good handle on the issue thanks to the objective science of chromosomes. Science is objectifying us in its theories while we do that through gender which for the Left generates some type of LGBTQ creature - while on the other end of the spectrum - a husband or wife - another socially constructed gender role. I am sure Camille Paglia would agree.
Property is clearly not a law of nature. It is a social construct expressing our subjective desire to be in control of our life, its limited span and of the production and consumption of goods that support it. Animal in the forest has no career, no property, does not make a living and leaves no estate to its descendants. Property is a subjective construct which we make function with the force of reality. Objective force of reality - in this case known as economic power. I am sure Mises would understand.
For the classical liberal and libertarian postmodernism should not be a challenge but a perspective and a methodology to see the issue of political and human rights as the right of the subject to constitute the objective world.