Chomsky expounded on the ideas above in Manufacturing Consent
Yes he and Herman spent lots of time explaining themselves in that book, and even during his book tour Chomsky spent hours defending his Pol Pot defense and denial, now saying "The case in Cambodia was, of course, a nefarious bloodbath. That was the bad guys doing it." Notably, this is not a phrase that he or Herman uttered until well after it became apparent that Pol Pot, was in fact carrying out a genocide.
In MF and his book tour, Chomsky goes to great pains to now explain that they were trying to draw a comparison between the Cambodian massacre and the East Timor massacre:
"What we said about Cambodia, however, that elicited a huge new outrage over the fact that we were defending Pol Pot. Well, we were defending Pol Pot by saying that he was carrying out a slaughter comparable to the major slaughter that the United States was backing in Indonesia, and pointing out that, in fact, that was the picture given by American intelligence, the only people who knew anything about it, and then talking about the way this was distorted in the interests of the propaganda system."
The problem that Herman and Chomsky faced, however, that the words "East Timor" or "Indonesia" do not appear anywhere in the Nation article. Faced with this new criticism, Chomsky shut up about Cambodia for about 20 years.
Manufacturing Consent: The Political Economy of the Mass Media