Dave, I'd like to touch on a central point that risks being overlooked.
Yes, Rand and her followers are generally - and as Mr Valliant demonstrates with his "Objecto-empiricism", even hilariously - ignorant of science. This is basically admitted every time they attempt to ring-fence some of her (and their) absurdities by appealing to a "philosophic" context, rather than a scientific one.
But the key point is this: basically Rand believed philosophy should quite literally set the terms for science (she says this quite clearly in the ITOE, in a remarkable passage where she insists that philosophers like herself will tell scientists the "proper" meaning of the words they use**). Philosophy is always in control; it might refute science; but it can never be the other way around. Philosophy is the master discipline - with Objectivism at the summit of that - from which "true" science (as well as ethics, politics, aesthetics etc) flows.
One can easily see the seduction here. The dream of the kind of intellectual power that allows you to make pronouncements over what is "proper" to even disciplines that you are ignorant of, has, like other more obvious dreams of power, perennial appeal. Further, it is a power that seems remarkably easily achieved; for it is basically very easy to play with words, as the Aristotelian method of definition that Rand adopted inevitably leads to (just as it lead to the scholasticism of the Middle Ages). This in turn empowers people like Mr Valliant to rock up to a science forum and begin instructing all and sundry as to what does and does not constitute "empirical" evidence. (And surely enough, with sufficiently determined sophistry, we see the determinist arguments from the massive empirical successes of physics and chemistry become dismissed as "empty arguments from authority", and his personal "introspections" promoted as both "empirical" and even "objective.")
It could be that Mr Valliant merely thinks it is Opposites Day here at Dawkins.net. However, I think there's a bigger story here. I conjecture that it is this underlying dream, and its accompanying scholastic methodology, that accounts for this peculiar picture of a movement ostensibly dedicated to reason, freedom, science, and productivity exhibiting, as you have already noted, so many alarming tendencies in the reverse direction.
*Even this appears to be incorrect, as Beckmann was apparently merely influenced by Rand. More about Beckmann here
**see pp289/290 "Introduction To Objectivist Epistemology"