You're on the right track:
Bull -- understanding frames of reference, ideological expectations, methods of questioning data
Cow -- having memorized data
Bull is clearly more valuable than cow, especially in a world where data itself can simply be looked up whenever it is needed. To be able to write the former, you need to be able to think critically and to show awareness of the prevailing paradigms. Cow only requires you to have turned yourself into a biochemical tape recorder, able to repeat back class notes or textbooks verbatim. Of course, bull has its dark side to, not much addressed in the essay. So, in the example given in the essay, the science student can ace the sociology essay because he is smart enough to guess, from the book titles, what the general topics of the books are about. He knows the general biases that govern the field and that tend to slant the teachings of sociology professors. He can therefore guess both what the books likely said about their topics, and what the professors want to see in the essay discussion. The data upon which the books rested isn't really all that important -- it was likely cherry picked and massaged to support the "right" conclusion anyway, as that's what happens when a field is dominated by biased ideologues. Indeed, many professors, especially in the humanities, share the relativistic view of the author of the essay, in which facts aren't facts, but merely things to be interrogated and twisted until you get the result you believe in. Of course, this is generally only held to be true when you don't like the facts. When the facts support your position, then they are inviolable and those who hold contrary views are ignoramuses.
The above should give you an idea of how someone might go about responding to the claim you have to respond to. Of course, your own response might be very different . . .
Sean, EssayForum.com