"Those who dont build must burn" what do you think this quote means?

From the text, we can infer that Faber is says that those who do not acitively try to save the books..... may as well be burning them. There is no grey area..... it's black and white. This same type of analogy is often used to describe those who knew what the Nazis were doing to the Jews during the Holocaust, and yet, allowed it to happen without dissent.