Scientism is the understanding that science is the only valid form of knowledge . It's an ideology and permeates real scientific circles. When thinkers whose understanding is colored by this ideology their defense of science against valid ordinary critique is ideological and programmed, We can always spot this kind of thinking immediately because they inevitably see any valid criticism as an attack upon the very notion of science, This tendency to think of science as some fragile sacred truth that dare not be questioned is emblematic of ideological reverence, An example bof this attitude is found in the essay by Marcel Kuntz is at the Laboratoire de Physiologie Cellulaire Végétale, CNRS/Université Joseph Fourier/CEA/INRA in Grenoble, The essay entitled "The Postmodern assault on Science"
Kuntz tells us "Postmodernist thought is being used to attack the scientific worldview and undermine scientific truths; a disturbing trend that has gone unnoticed by a majority of scientists. Postmodernism undermines all truth. Kuntz wants to privilege his view as THE TRUTH! You Know I believe in truth but I don't believe science is the one and only truth,
The scientific method has been the guiding principle for investigating natural phenomena, but postmodernist thought is starting to threaten the foundations of the scientific approach. The rational, scientific view of the world has been painstakingly built over millennia to guarantee that research can have access to objective reality: the world, for science, contains real objects and is governed by physical laws that existed before our knowledge of these objects and laws. Science attempts to describe the world independently of belief by seeking universal truths, on the basis of observation, measurement and experimentation.  I agree with several aspects of this view point, I think science is the chief means of understanding the naturalistic workings of the world and that it does supply a less subjective means of understanding the regularities of the law-like framework of the universe's behavior. Yet when we frame it as "objective," even though it can be called that in a relative way, we set up the validity of the Postmodern critique, it is this very swaggering claim to the one and only truth that postmodernists are reacting against. The claim that science gives us access to "objective reality" is a metaphysical claim that is guaranteed to open up not objectivity but philosophical critique, The statement about universal truth is a dead giveaway. God's love is a universal truth, There might be a realm of the forms where Universal truths are housed for all we know. This clam impinges upon all metaphysical claims and thus is itself a metaphysical assumption. That makes it fair game for philosophy.
The postmodernist school of thought arose to question these assumptions, postulating that claims about the existence of a real world—the knowledge of which is attainable as an objective truth—have only been relevant in Western civilization since the Enlightenment. In recent decades, the movement has begun to question the validity of claims of scientific truth, whether on the basis of their belonging to larger cultural frames or through heavy criticism of the scientific method.  Postmodernism did not arise solely to question the assumptions of science and objective evidence, That's an unfair generalization. That's the hallmark of his whole attack because it fails to distinguish between levels of postmodern thought, it lumps all philosophical critique of science into the same pile as the most extreme Postmoderns.
When he gets specific the first one he goes after is Thomas Kuhn. Kuhn is probably the most famous and the most legitimately accepted and admired thinker to be labeled "Postmodern." If we must label him for my money I would label him Postmodern light,
Thomas Samuel Kuhn (1922–1996) is one of the most influential philosophers of science of the twentieth century, perhaps the most influential. His 1962 book The Structure of Scientific Revolutions is one of the most cited academic books of all time. Kuhn's contribution to the philosophy of science marked not only a break with several key positivist doctrines, but also inaugurated a new style of philosophy of science that brought it closer to the history of science. His account of the development of science held that science enjoys periods of stable growth punctuated by revisionary revolutions. To this thesis, Kuhn added the controversial ‘incommensurability thesis’, that theories from differing periods suffer from certain deep kinds of failure of comparability. "The concept of paradigm shift proposed by Thomas Kuhn in his famous book, The Structure of Scientific Revolutions (1962;), has also given weight to the critics of science and of its pretension to understand reality. If science is not a gradual process of accumulation of knowledge, but rather subject to sudden “revolutions” that overwhelm outdated theories, they argue, how can one trust scientific knowledge?" (from Kuntz, Op cit)
Who are they? Who are these faceless critics of science who are out to steal reality? He imagines this rival group of knowledge preachers with their own metanarrative to sell. That Is ideology pure and simple. It's saying my metanarrative is true not yours.
I don't believe he has read Kuhn, Here are a couple of red flags. First, Kuhn does not say there's a sudden change, Revolutions don't have to be sudden. The metaphor there is political not temporal. In fact Kuhn's theory states that the shift happens when the paradigm can no longer absorb anomalies that can can a long time for the anomalies to pileup. He says that for an individual researcher it can come as a sudden realization but it's not coming overnight in terms of what's going in the field as a whole. When Kuhn says it's not a gradual accumulation of knowledge, he doesn't mean these questions haven't been floating around for a long time, but that scientific knowledge is not cumulative. It's not a long slow piling up of facts until we find truth. Scientific knowledge can come in an instant; he's talking about regular scientific knowledge. Another red flag his rhetorical question how can one trust scientific knowledge? That is his take on Kuhn. Kuhn himself does not say that. Kuhn never goes after science. He is not a science baser. He's not trying to foster doubt about science.
"If, as according to Kuhn, scientific revolutions are also political upheavals in scientific policy, it is easy to understand why Kuhn's theory has attracted so much attention in a period that calls into question the established political order in the Western world."  So here wants to make postmodernism some kind of communist-like threat to peace and civilized order, That strikes me as red Baiting, Is that a bad thing? Questioning the political order?
I find that extremely simplistic, lacking in any specificity that makes it applicable to Kuhn, Kuhn is very specific about how defense of a paradigm is like a topological battle. That is why he calls it the scientific revolutions because defense of the old paradigm is like a political regime defending against a revolution,
Then he starts talking about the strong programme as tough Kuhn is in that movement, He was not. The strong programme is the extreme end of postmodernism that does seek to overturn all truth and all science and fits the stereotype, It was largely based in Edinburgh with thinkers like David Bloor.  Then he slides into talking about the ‘strong programme' in such as way as to convey the impression that it; related to Kuhn, He also milables and thus castigates other thinkers such as Ian Hacking,
Several deconstructionist thinkers, such as Bruno Latour and Ian Hacking, have rejected the idea that the concepts of science can be derived from a direct interaction with natural phenomena independently of the social environment in which we think about them. The central goal of science, defining what is true and what is false, becomes meaningless they argue, as its objectivity is reduced to ‘claims' that are simply the expression of one culture—one community—among many. Thus, all systems of thought are different “constructs” of reality and all additionally have political connotations and agendas.
He starts out here Identified Hacking as a deconstructionist. Hacking is certainly not a decon. Hacking says he's a Cambridge analytic philosopher.  He has been lauded for his scholarship. I am a big fan of his. He is clearly a major historian of sicced. If he can be labeled in the postmodern vein it would be as a Faulcaultian not a Derridan, That's very different,  Faucult had no ax to grind against science.
The generalizations in implacable and them vs us mentality against what should be considered a valid academic quest for knowledge is indicative of the ideological basis of geneticist thinking, That gives credence to the postmodern critic of the meta narrative,
all sources acceded 5/2/17
 Marcel Kuntz,"The Postmodern assault on Science" EMBO Rep v.13(10); (Oct)2012URL
Kuntz is at the Laboratoire de Physiologie Cellulaire Végétale, CNRS/Université Joseph Fourier/CEA/INRA in Grenoble,
 Alexander Bird,, "Thomas Kuhn", The Stanford Encyclopedia of Philosophy (Fall 2013 Edition), Edward N. Zalta (ed.), First published Fri Aug 13, 2004; substantive revision Thu Aug 11, 2011 URL = .
 Thomas Kuhn,
 Kuntz op cit
 David Bloor, "The strengths of the strong programme." Scientific rationality: The sociological turn (Springer Netherlands, 1984) pp. 75-94.
Kuntz, Op cit
 Ian Hacking quoted in "Who Are you? The Biosocial Being Ian Hacking Ioan Davies memorioal lecture, (4/14/17) held at university of Troomnto, URL: http://www.yorku.ca/ioantalk/lecture2011.htm
Karen Grandy, "Ian Hacking". The Canadian Encyclopedia. Retrieved 2016-06-10.
Thomas P. Kasulis, Robert C. Neville, John Edwin Smith The Recovery of Philosophy in America: Essays in Honor of John Edwin Smith