Word Choice. Hope this helps!
Answer: If people knew what was happening in the other parts of Panem then they might turn against the capital knowing the horrible living conditions in which say Katniss’s lives in. What people don’t know doesn’t hurt them. So it benefits the Capital by the amount of control they have.
In the lines from Shakespeare's "The Tragedy of Macbeth," Lady Macbeth is talking to herself while she is sleep walking. She feels so guilty that she cannot sleep properly. In that respect, she means that she and Macbeth do not need to fear anything because they are so powerful that nobody will believe they are responsible for killing Duncan. However, she does not actually think so - she is only trying to convince herself of it because she is under the impression that everybody is suspicious of Macbeth.