Beatty would probably give new recruits a speech very similar to the one he gave Montag. You can use some of these arguments as well as quotes from Beatty to include in your speech.
When Montag asks Beatty if firemen always put out fires, he tells him that the service was established in 1790, and the first fireman was Benjamin Franklin. You can also include the speech Beatty gave the woman who wanted to die with her books.
None of those books agree with each other. You've been locked up here for years with a regular damned Tower of Babel. Snap out of it! The people in those books never lived. (part 2)
Other arguments he made is that the government did not censor books, but the people prefer to be happy, and happiness comes from being comfortable. Censorship came from marketers not wanting to offend any minority. Universities closed from lack of students. The government did not have to close them. The fire deparment was just keeping the peace.