that FAQ Section 4.3.5 rebuts is that of the "left gatekeepers." This theory holds that the leftist media complex is structured in much the same highly centralized way that the right-wing, or "mainstream" media complex is. F'rinstance, it's held that the CIA funds George Soros and that Soros in turn, funds Z Magazine. The "proof" is that Z doesn't feature any theories about 9-11.
First off, the proof used by The Nation Magazine to construct the National Entertainment Media chart was actual ownership, ownership that can be catalogues and defined and quantified. "Left gatekeepers" uses investments, a much more difficult and complicated measurement. If "left gatekeepers" had a whole staff of people to gauge this, it might have amassed real proof. As it is, it's just one guy doing all of the research. If I were a prosecutor accusing Z Magazine of doing the bidding of George Soros, I'd say "gatekeepers" has the beginnings of a decent case, but that it has a long way to go.
Second, it's clear from Faq Section 4.3.5 that there may indeed be alternate theories as to why lefty media folks don't all publish 9-11 theories. It may just be because they just don't like getting into those areas and don't want to be associated with those who do.