The way in which Beatty treats Montag is very ironic in my opinion. The irony is that Beatty is choosing to arrest his own fireman, Montag, for reading books when Beatty, himself, as read books as well. This is evident because he quotes passages from books he has read to Montag at the firehouse and before Montag kills him. He taunts him with quotes from Shakespeare and calls Montag a fool for his actions. This is ironic because the very actions he is claiming to arrest Montag for are the same actions he committed at an earlier date. He has Montag burn his own home and watches him do it all the while taunting him for choosing to hide and read books.