Fraser: Many blame the media, which are intertwined with the power blocs of politics and business (an increasingly concentrated planetary business) and which do now and then function as propaganda machine and censor. But most of the time the media operate more insidiously than that, narrowly circumscribing what is allowable and thereby what is verboten in public debate, what is legitimate and what is outré, what is to be taken seriously and what is to be coolly dismissed. They invoke the sounds of silence without gagging anyone.