Unable to appeal either to fact or logic, Rand appealed to an old standby: sheer intimidation. If she couldn't persuade with sweet reason, she would resort to browbeating instead. Here's how it works. Rand begins by arbitrarily declaring that man's mind is under attack and needs to be defended.
To negate man's mind, it is the conceptual level of his consciousness that has to be invalidated. Most philosophers did not intend to invalidate conceptual knowledge, but its defenders did more to destroy it than did its enemies. They were unable to offer a solution to the ‘problem of universals,’ that is: to define the nature and source of abstractions, to determine the relationship of concepts to perceptual data—and to prove the validity of scientific induction.... The philosophers were unable to refute the witch-doctors claim that their concepts were as arbitrary as his whims and that their scientific knowledge had no greater metaphysical validity than his revelations. [FTNI, 30]
By "invalidating" conceptual knowledge, modern philosophers opened the door to mysticism, altruism, and collectivism:
It is the philosophy of the mysticism-altruism-collectivism axis that has brought us to our present state and is carrying us toward a finale such as that of the society presented in Atlas Shrugged. It is only the philosophy of the reason-individualism-capitalism axis that can save us and carry us, instead, toward the Atlantis projected in the last two pages of my novel.
By framing the debate in these extravagent terms, Rand is able to position herself as the champion of "conceptual knowledge" while at the same time framing her critics as those who (whether unwittingly or not) are leading Western Civilization of a cliff. Hence, anyone who challenges, criticizes, or even doubts Rand's "validation" of conceptual knowledge is contributing to the destruction of civilization. For Rand, epistemological errors, even of the most trivial sort, are fraught with danger. Consider the following exchange from Rand's epistemological workshops:
Prof. A: ...length doesn't exist per se in reality. Length is a human form of breaking up the identities of things.
Ayn Rand: Wait a moment, that's a very, very dangerous statement.
Claiming that the proposition "length doesn't exist" is a "very, very dangerous statement" appears rather far-fetched. What evidence does Rand have to support the contention that uttering such a sentence will cause any harm, either to the person who utters or those who hear it? It's just a string of words, without reference to anything practical or consequential: mere speculative patter over obscure technical issues that hardly anyone cares about. It is only dangerous if one accepts Rand's improbable notions about human beings being the playthings of their premises. Even then, it seems a bit of a stretcher.
The deeper problem is that Rand casts her entire validation of concepts under this cloud of danger. Epistemological errors are dangerous because they can lead to an attack on man's conceptual faculty, which can lead to a "negation" of man's mind. Hence Rand tries to intimidate us into accepting her validation of concepts. This stategy, however, is based on a logical fallacy: namely, the argumentum ad consequentiam fallacy. Rand is trying to convince us of the truth of the Objectivist epistemology on the basis of the alleged consequences of following non-Objectivist epistemologies. But this appeal is wrong in a number ways. It is wrong in its assumption that people follow specific epistemologies; it is wrong to assume that there are any consequences to expressing allegiance to this or that speculation about human cognition; and it is wrong in assuming that the alleged consequences of a doctrine can prove anything about the the doctrine itself.
In short, it is intellectually perverse to assume that criticism of Rand's epistemology is either (1) motivated by a desire to destroy man's mind or (2) will by necessity lead to the destruction of man's mind, irrespective of motives. These two implicit premises must be challenged from the start. Nothing is really at stake in a discussion of the Objectivist epistemology beyond the truth of Rand's various speculations about human cognition.