I think the best way to answer this is to say that Faber blames himself and other people like him for the burning.
There is a quote I've seen from someone who survived the Holocaust -- he wasn't a Jew but was another kind of person that Hitler didn't like. He said something to the effect that when the police came for other people, he didn't defend them and by the time the police came for him, there was no one to defend him.
This is what Faber is saying about him and books. He says that he was an innocent person back when the book burning type of thing started. He says he could have spoken out against it and maybe stopped it. But instead he was afraid to speak out, and then it was too late.
In Bradbury's dystopian society, it is illegal to own literature and firemen burn books, instead of putting out fires. When Montag visits Faber's home in hopes of gaining insight into the various books that he owns, he begins to discuss the firemen system with Faber. Faber initially admits that he is partially responsible for the firemen structure that has become an essential aspect of society. Faber tells Montag,
I saw the way things were going, a long time back. I said nothing. I'm one of the innocents who could have spoken up and out when no one would listen to the 'guilty,' but I did not speak and thus became guilty myself.
In addition to taking partial responsibility for allowing book burning to take place, Faber also blames the passive citizens. Faber tells Montag,
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.
The public has no desire to read literature and feels that books are unnecessary. The vast majority of the citizens stopped reading on their own accord and support book burning. Overall, Faber blames himself and the citizens of the dystopian society for allowing the firemen system to thrive.