The dialogue reveals that Kenneth wants to control the situation (1).
You can reach this conclusion by looking at the following clues in the text.
His tone is composed, as opposed to Xavier's who is more emotional. In addition to the stage directions telling us that Xavier is "alarmed," he speaks in successive short sentences, often made up of only one word ("Great. Thanks.") or with exclamation marks ("Oh, man, this could be disastrous!"). In an attempt to calm Xavier down or to assert his confidence over him, Kenneth uses longer sentences, with a more rational tone: " I waited until Ms. Wilmore went to help somebody, then I sneaked the book off the shelf and copied the thing."
Kenneth uses the imperative mode to give orders to Xavier: "Calm down." / "Just sit down, okay?"
Kenneth is in charge of the action and intends to stay that way. He is the one who did the sneaking, copying, and replacing work, and then wants to keep control by refusing to give the document to Xavier ("Not if I don’t give it to you") and reading it to him himself ("I’ll read this thing to you").
