In Fahrenheit 451, Granger and his followers (the book people) are heroes because they voluntarily left society in order to keep literature alive. The world Montag lived in (and eventually escaped from) suppressed individualism and active thinking. To ensure they kept the masses from becoming aware of their oppressed state, the firemen burned all literature. The strategy was to keep all enlightening or inspiring knowledge and literature out of the public's hands. To supplement this suppression, the public was encouraged to sit back and passively watch the shows on the parlour walls. And for some, like Mildred, they would live vicariously through the lives of the characters or even treat the characters like family.
Granger and his followers recognized that this way of living demoted the public to living lives of thoughtless automatons. To preserve inspiring ideas by memorizing books, Granger and his followers have risked their lives and must always live on the outskirts of society for as long as this suppression of literature exists.