The book deals with a lot of themes about censorship, so naturally you would think censorship is one of his main points or themes he is trying to convey in the book. Strangely enough, censorship was not what he intended the book to be about. According to Bradbury, the book is about media and how it dumbs down the nation.
I wasn't worried about freedom, I was worried about people being turned into morons by TV. We've never had censorship in this country, we've never burned books...
Fahrenheit's not about censorship, it's about the moronic influence of popular culture through local TV news, the proliferation of giant screens and the bombardment of factoids. All the popular programs on TV, the competition programs, they don't give you anything but factoids. They tell you when Napoleon was born, but not who he was. So it doesn't matter about the date. You should never memorize dates, to hell with it. So we moved into this period of history that I described in Fahrenheit 50 years ago
(source: Bradbury on Censorship/Television)
In fact, he even gets angry when readers insist the book is about censorship.
Weller: have you encounted academic misinterpretation of your work?
Bradbury: I was lecturing at Cal Fullerton once and they misinterpreted Fahrenheit 451, and after about half an hour of arguing with them, telling them that they were wrong, I said, “Fuck you.” I've never used that word before, and I left the classroom.
(Source: Listen to the Echoes)
Even though a lot of the book seems to be about censorship, you can see elements of "Media dumbing people down" in it. For example,
Montag has trouble getting along with his wife because she is consumed with media. TV, telephone, plays, etc.
Clarisse seems to be one of the few characters that isn't caught up in the cycle of endless consumption. She plays outside, and is very curious. Beatty says about her:
Beatty smiled. "Here or there, that's bound to occur. Clarisse McClellan? We've a record on her family. We've watched them carefully. Heredity and environment are funny things. You can't rid yourselves of all the odd ducks in just a few years. The home environment can undo a lot you try to do at school. That's why we've lowered the kindergarten age year after year until now we're almost snatching them from the cradle. We had some false alarms on the McClellans, when they lived in Chicago. Never found a book. Uncle had a mixed record; anti?social. The girl? She was a time bomb. The family had been feeding her subconscious, I'm sure, from what I saw of her school record. She didn't want to know how a thing was done, but why. That can be embarrassing. You ask Why to a lot of things and you wind up very unhappy indeed, if you keep at it. The poor girl's better off dead."
Beatty directly states that the firemen came about when the nation started caring more about quick and shallow consumption (TV) than deep, slow, meaningful consumption (books). Here's a pretty long quote where Beatty is talking to Montag about the origins of the firemen:
Beatty puffed his pipe. "Every fireman, sooner or later, hits this. They only need understanding, to know how the wheels run. Need to know the history of our profession. They don't feed it to rookies like they used to. Damn shame." Puff. "Only fire chiefs remember it now." Puff. "I'll let you in on it."
Beatty took a full minute to settle himself in and think back for what he wanted to say. "When did it all start, you ask, this job of ours, how did it come about, where, when? Well, I'd say it really got started around about a thing called the Civil War. Even though our rule-book claims it was founded earlier. The fact is we didn't get along well until photography came into its own. Then--motion pictures in the early twentieth century. Radio. Television. Things began to have mass."
Montag sat in bed, not moving.
"And because they had mass, they became simpler," said Beatty. "Once, books appealed to a few people, here, there, everywhere. They could afford to be different. The world was roomy. But then the world got full of eyes and elbows and mouths. Double, triple, quadruple population. Films and radios, magazines, books leveled down to a sort of paste pudding norm, do you follow me?"
"I think so."
Beatty peered at the smoke pattern he had put out on the air. "Picture it. Nineteenth-century man with his horses, dogs, carts, slow motion. Then, in the twentieth century, speed up your camera. Books cut shorter. Condensations, Digests. Tabloids. Everything boils down to the gag, the snap ending."
"Snap ending." Mildred nodded.
"Classics cut to fit fifteen-minute radio shows, then cut again to fill a two-minute book column, winding up at last as a ten- or twelve-line dictionary resume. I exaggerate, of course. The dictionaries were for reference. But many were those whose sole knowledge of Hamlet (you know the title certainly, Montag; it is probably only a faint rumour of a title to you, Mrs. Montag) whose sole knowledge, as I say, of Hamlet was a one-page digest in a book that claimed: 'now at least you can read all the classics; keep up with your neighbours.' Do you see? Out of the nursery into the college and back to the nursery; there's your intellectual pattern for the past five centuries or more."
"Speed up the film, Montag, quick. Click? Pic? Look, Eye, Now, Flick, Here, There, Swift, Pace, Up, Down, In, Out, Why, How, Who, What, Where, Eh? Uh! Bang! Smack! Wallop, Bing, Bong, Boom! Digest-digests, digest-digest-digests. Politics? One column, two sentences, a headline! Then, in mid-air, all vanishes! Whirl man's mind around about so fast under the pumping hands of publishers, exploiters, broadcasters, that the centrifuge flings off all unnecessary, time-wasting thought!"
"School is shortened, discipline relaxed, philosophies, histories, languages dropped, English and spelling gradually neglected, finally almost completely ignored. Life is immediate, the job counts, pleasure lies all about after work. Why learn anything save pressing buttons, pulling switches, fitting nuts and bolts?"