Certainly, Sorkin is known for his flowing dialogue (or monologues, as it were). And as for the substance of those words intended to be spoken, there's this:
The New Yorker - Broken News: The artificial intelligence of “The Newsroom.”
And yet, all sorts of experienced speechwriters could have written Will's dialogue. Indeed, standing alone, much of the dialogue that Sorkin crafts - especially the speeches like that one - is over-the-top, even comical, and any actor who can sell that dialogue as serious dialogue is earning his/her pay.
The irony of Sorkin, "the master of dialogue", is that the make or break of his writing isn't the dialogue, it's the story, it's how he gets us to this moment and then the next one.