Why is Faber an outcast in Fahrenheit 451 by Ray Bradbury?

In Fahrenheit 451, Faber is portrayed as an outcast in a number of ways.

First of all, Faber is an outcast because he has not embraced the new regime of his society in which books are forbidden. As a former professor, Faber cannot let go of his love of books and learning. This makes Faber suspicious of others. We see this when Montag calls him to ask about the Bible:

This is some sort of trap! I can't talk to just anyone on the phone.

Secondly, Faber is an outcast because he does not have the television broadcast directly onto his parlour walls. As he tells Montag:

As you see, my parlour is nothing but four plaster walls.

Moreover, Faber is completely opposed to all types of entertainment which are glorified by his society. He believes that entertainment, like television and fast driving, are just designed to distract people's attention and force them to absorb society's messages:

The televisor is 'real.' It is immediate, it has dimension. It tells you what to think and blasts it in.

Finally, Faber is an outcast because he wants to rebel. Despite his initial cowardice, Faber finds an ally in Montag and helps him where he can. Faber offers to make contact with a printer, for example, and gives Montag an earpiece to wear so he can talk to Montag when he goes to face Beatty.  Faber also helps Montag toward the end of the novel, arranging to meet with him in St. Louis after he has fled the society.

Meeting Montag, then, transforms Faber from an outcast into a rebel, ready to contribute to the destruction of the old society and the creation of a new, liberated world.