In the post James L. Brooks on Chayefsky, Brooks is quoted as having great admiration for Chayefsky’s monologues in Network and Hospital. This is what screenwriter and former USC professor Irwin R. Blacker had to say on the topic of speeches in book The Elements of Screenwriting (which was first published in 1986 shortly after his death).
There was no need for a speech against was in All Quiet on the Western Front.
There was no need for a speech against vigilante justice in The Ox Bow Incident.
There was no need for a speech against money-making evangelicalism in Elmer Gantry.
Each film made its point without any characters declaiming on the subject. The subject of the film and the way the film is constructed should convey sufficient message. Guess Who’s Coming to Dinner? was diminished by its undramatic speeches about tolerance: no character in Death of a Salesman discussed the eroding quality of the American Dream gone sour. As Samuel Goldwyn is reputed to have said, ‘Messages are for Western Union.”
So even if Chayefsky and Shakespeare pulled off big speeches doesn’t mean that most writers should or can.