Postmodernists are as capable of dogmatism as any other group of human beings might be. The tenor of this article points towards it: an unsubstantiated--unsubstantiable--insistence on the correctness of a point of view that is in the end wholly subjective.
The postmodern perspective has provided insights that are, to me, perfectly valid. For instance, I accept that 'objective truth' is a human impossibility, in the sense of any person being uninfluenced in any cognitive undertaking by extraneous subjective factors.
Even so, postmodernists have erred to the extent that they have gone from that insight to a generalized condemnation of rationality: 'the rational'. Like 'Enlightenment' thinkers did, they have continued to equate ideology, which is based on (secular) beliefs, with rationality. Beliefs are completely non-rational, totally subjective. We can reason from beliefs, but the product of that reasoning is at bottom as subjective as the belief itself can only be.
Applying the rational faculty to material existence is what scientists do. As individuals they cannot escape subjective influences. Even so, the scientific project is not purely subjective in the way that beliefs, therefore ideologies and theologies, are. The products of science can therefore be universally valid for human beings in a way that no conclusion following from reasoning from any belief ever could be. Any knowledge gleaned from experience of material existence has that potential.
One thing 'Enlightenment' thinkers got completely correct is that justice--real justice--requires universality. What we need as a species is to recognize that our rational faculty, applied to material existence, is the only possible source of the universal commonality justice requires.
That is to say, the ethic of justice can only be an 'ought from is' . Applying that ethic to the governance of society would take us "Beyond Liberalism" (both linked articles here in Medium, but not behind the paywall).
Even if a person rejects the necessary universality of this ethic, a person could advocate for it for the governance the society in which that person lives as legitimately as anyone could advocate for any other ethic. For example, this ethic involves a requirement of mutual respect, and a requirement of mutual respect does follow from a belief in some moral equality among all human beings. In the contest of power between liberty and equality that is rending Liberalism asunder, “Equality Is All We Need” (also in Medium but not behind the paywall).