Faber says he bears some responsibility for the dismal state of the world. What is the source of fabers guilt?

Faber's guilt comes from his inability to act and his shyness, he is way too hard on himself though, and there's so much only one person can do, even as he faced the odds he did.

His cowardice is really the source of his shyness, he can't even go to Montag printer friend without having him on the earpiece, he is one of the few intellectuals left in their society, he's not very responsible though as they were fighting a losing battle.

And even if he had done more, it would've been meaningless because the minds of the people wouldn't had been swayed by the voice of one more person.