As noted above, the claim that the media are "adversarial" or (more implausibly) that they have a "left-wing bias" is due to right-wing PR organisations. This means that some "inconvenient facts" are occasionally allowed to pass through the filters in order to give the appearance of "objectivity"— precisely so the media can deny charges of engaging in propaganda. As Chomsky and Herman put it: "the 'naturalness' of these processes, with inconvenient facts allowed sparingly and within the proper framework of assumptions, and fundamental dissent virtually excluded from the mass media (but permitted in a marginalised press), makes for a propaganda system that is far more credible and effective in putting over a patriotic agenda than one with official censorship." [Ibid., Preface]
To support their case against the "adversarial" nature of the media, Herman and Chomsky look into the claims of such right-wing media PR machines as Freedom House. However, it is soon discovered that "the very examples offered in praise of the media for their independence, or criticism of their excessive zeal, illustrate exactly the opposite." [Ibid.] Such flak, while being worthless as serious analysis, does help to reinforce the myth of an "adversarial media" (on the right the "existing level of subordination to state authority is often deemed unsatisfactory" and this is the source of their criticism! [Ibid., p. 301]) and so is taken seriously by the media.
Therefore the "adversarial" nature of the media is a myth, but this is not to imply that the media does not present critical analysis. Herman and Chomsky in fact argue that the "mass media are not a solid monolith on all issues." [Ibid., p. xii] and do not deny that it does present facts (which they do sometimes themselves cite). But, as they argue, "[t]hat the media provide some facts about an issue. . . proves absolutely nothing about the adequacy or accuracy of that coverage. The mass media do, in fact, literally suppress a great deal . . . But even more important in this context is the question given to a fact - its placement, tone, and repetitions, the framework within which it is presented, and the related facts that accompany it and give it meaning (or provide understanding) . . . there is no merit to the pretence that because certain facts may be found by a diligent and sceptical researcher, the absence of radical bias and de facto suppression is thereby demonstrated." [Ibid., pp xiv-xv]