In Fahrenheit 451 what was Beatty's purpose in his speeches to Montag, and what do they reveal about the society?

When Beatty comes to Montag's house to talk to him, it is after Montag has shown a lot of hesitation and doubts regarding his job and what it entails.  The night before, Montag was really disturbed as Mrs. Blake chose to burn to death with her books; he doesn't show up for work that day as a result.  Beatty most likely noted his absence, and concluded, in combination with Montag's recent questions and hesitancy, that he was having a moral crisis of sorts, in regards to his job and to society.

Beatty is a the fire chief, and wants to keep Montag in line on this job; he notices Montag's discontent and comes to try to clear it up.  He realizes that Montag is a questioner, and so decides to answer all of his questions.  He feels that if he takes an all-disclosure approach with Montag, that if Montag knows the real facts behind his job, it will satisfy his curiosity and help him buck up and get back to work.  He wants to make Montag feel like he is on his side, that they are friends, and that he can be trusted; this way, he hopes that Montag turns back towards him instead of going down the path of rebellion.

He does this by letting Montag know he isn't alone in his crisis.  He states,

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.

He later alludes to the fact that he knows Montag has books, and tries to be nice, telling him that if firemen get an urge to read one, to see what it's all about, they give the guy 24 hours before he has to return it.  All of these techniques are Beatty trying to paint himself in a sympathizing, friendly, inclusive light, to try to turn Montag away from rebellion and questioning.

His revelations about society show how people's laziness and tendencies to get offended have aided and abetted the government in their subtle takeover of human thought.  It reveals that because people were unwilling to think, and were too willing to be offended by the contents of books, the government was able to step in and institute its fierce information control campaign, through the burning of books.

I hope that those thoughts helped; good luck!