This comment refers to the methods in which the society has eliminated books; instead of creating a dystopia immediately, the government slowly turned public opinion against books to the point where they no longer have the urge to read. This allowed the change to be gradual, finishing with a populace that is easily entertained and does not ask questions.
"Remember, the firemen are rarely necessary. The public itself stopped reading of its own accord. You firemen provide a circus now and then at which buildings are set off and crowds gather for the pretty blaze, but it's a small sideshow indeed, and hardly necessary to keep things in line."
(Bradbury, Fahrenheit 451, hrsbstaff.ednet.ns.ca)
Faber's larger point is that the "sideshow" of the firemen heroically burning the books, reminding everyone that books are illegal, is not actually necessary; the citizenry is all-too happy to avoid books as long as their needs and desires are met. The populace now exists as a controlled facet of government, not as individuals; they don't even think about books or dissenting opinions. Therefore, while the firemen are essential in keeping government control, the society is almost at the point where nobody remembers books, and all those who disagree are too scared to fight back. Once that point is reached, the firemen will be unnecessary because the populace itself will self-correct.