Why don't Granger and his friends want to make anyone angry in Fahrenheit 451?
Granger and his friends, the book people, offer a radically different strategy to the all-out violence that Montag tried in order to challenge the ruling regime of this dystopian world. As they admit to a rather shocked Montag, they burn books too, but only after memorising them and carrying around books, but in their memories. Granger explains his rationalisation of this strategy:
We read the books and burnt them, afraid they'd be found. Microfilming didn't pay off; we were always traveling, we didn't want to bury the film and come back later. Always the chance of discovery. Better to keep it in the old heads, where no one can see it or suspect it. We are all bits and pieces of history and literature and international law.
Granger presents his plan of a number of individuals walking around with books memorised and repressed in their brains, ready to pull out when society needs them again. He further develops his strategy, comparing it to the violence of Montag's approach:
But our way is simpler and, we think, better. All we want to do is keep the knoweledge we think we will need in tact and safe. We're not out to incite or anger anyone yet. For if we are destroyed, the knowledge is dead, perhaps for good. We are model citizens, in our own special way; we walk the old tracks, we lie in the hills at night, and the city people let us be. We're stopped and searched occasionally, but there's nothing on our persons to incriminate us. The organization is flexible, very loose, and fragmentary.
So, the answer to your question is, because of the way Granger and his people have chosen to preserve texts, there is no point trying to provoke an outright confrontation, because the long term goal is the preservation of important pieces of literature. The death of any book person means the death and ultimate loss of that knowledge too. Thus it is much better to hide away and live quietly, not getting into trouble, until such a time when that knowledge will be needed again.