In Part One of the novel, Faber admits to Montag that he is a coward. Faber feels this way because he saw how "things were going" and he didn't do anything about it. In other words, he did not speak up against censorship when the government first introduced it. Since then, he has lived in relative isolation, keeping to himself and avoiding conflict with the government and the firemen in particular.
Faber quickly overcomes his cowardice, however, when he realizes that Montag is a potential ally and not his enemy. He gives Montag a homemade communication device, for example, so that he is not alone against Beatty. He also volunteers to see an "unemployed printer" about creating new books to plant in the homes of other firemen. Montag has, therefore, rejuvenated Faber and helped him to realize that staying afraid and remaining silent are no longer viable options.
Finally, in Part Three, when Montag is fleeing the Mechanical Hound, Faber proves his strength by providing him with clothes and a strategy to exit the city. He also arranges to go to St. Louis to see a retired printer. Despite the dangers, Faber stays committed to his and Montag's plan to bring down the fireman system. Sadly, Faber's fate is never revealed and the reader is left to wonder if his newfound strength guaranteed his survival.
Faber calls himself a coward when he is speaking to Montag, even before the planting books scheme came up at all. He states,
"You are looking at a coward. I saw the way things were going, a long time back. I said nothing...and when they finally set the structure to burn the books, using the firemen, I grunted a few times and subsided...now it's too late."
So, back when the trends started changing to where firemen were burning books, Faber was a coward because he said nothing about it; he didn't fight, he didn't start a resistence movement, and he didn't rebel. He cowered at home, doing nothing, in order to save himself. Also, when Montag met him at the park the first time, he was super suspicious and in denial about anything in regards to books; later, when Montag calls him he also cowers and hangs up the phone denying knowing anything about the bible. So, Faber has had a history of backing down and playing quiet for survival's sake; he feels a coward for it. However, it is that background that primes him perfectly for action when Montag steps into his life. He is ready to act and vindicate himself from his past acts of cowardice.
Yes, because he uses other innocent bystanders to do his dirty work.