In order for Montag's society to get to the point where books are being burned, it was a slow, steady process of change. It was people's changing attitudes towards books, intelligence, and other people that led the process about. Beatty explains the steps that led to the firemen's existence (as known in Montag's society). He states that one reason that books becamae unpopular is because they had content that offended the "minorities" in their civilization. Everyone was offended by something in the books, so, burning them made it so that people don't have to read "offensive" material. Beatty states,
"Someone's written a book on tobacco and cancer of the lungs? The cigarette people are weeping? Burn the book."
So many people found something offensive that all books should just be burned so that people can be happy; and that is where the firemen come in.
Beatty also stated that their society burned books to try to make everyone equal, so as to make everyone feel better about themselves:
"the word 'intellectual' became the swear word it deserved to be...you remember the boy in your own school class who was exceptionally 'bright'...and wasn't it this bright boy you selected for beatings...after hours?"
So, books made people feel stupid, because other people read them and were smarter as a result; so, burn books in order to create "equality" in intelligence so that no one has to feel stupid.
There are other reasons that Beatty stated for burning books; one is because people simply stopped reading them at all out of laziness. Books got condensed and shortened so people could "read" them faster; pretty soon, they just disappeared because people didn't want to make the effort.
The government went along with all of this because a non-reading society is a non-thinking society that is easier to control. They jumped on society's tendency to not think and used it to keep them in control and unrebellious. I hope all of those explanations helped!
Your question is not specifically answered in the novel.
If a person can read, a person can think. If a person can think, a person can decide for him or herself whether or not the system of government is good or bad.
The screens frequently mentioned in the novel are a type of network that watches the citizens while providing a type of entertainment/propaganda. Bradbury is trying to warn people of the mind-numbing effects of television. Bradbury is warning people of the hypnotic propaganda potential of television.
Mildred and her friends are mesmerized by the programs they watch in the television parlor.(http://www.enotes.com/fahrenheit-451/themes)
The people have given up their "rights" to books in order to be protected from "fire". The revisionist historians in the novel have rewritten history to show that famous people in history, such as Ben Franklin, have been fire-starters.
Bradbury uses a gross exaggeration to let the readers know that fear is the main tool of the propagandists in their efforts to control the thoughts of the populace.