How does Scout in To Kill a Mockingbird show two sides?

That the young narrator of To Kill a Mockingbird goes by the nickname "Scout" is very appropriate. In the story, Scout functions as both questioner and observer. Scout asks tough questions, certainly questions that aren't "politically correct," but she can ask these questions because she is a child. As a child, Scout doesn't understand the full implication of the things happening around her, making her an objective observer and a reporter in the truest sense.
You should keep in mind, though, that To Kill a Mockingbird really presents two Scouts: the little girl experiencing the story and the adult Jean Louise who tells the story. The woman relating the story obviously recognizes that her father is exceptional. However, the child Scout complains "Our father didn't do anything . . . he never went hunting, he did not play poker or fish or drink or smoke. He sat in the living room and read." The child Scout marvels that her father knew she was listening to his conversation with Uncle Jack; the adult Jean Louise marvels that he wanted her to overhear the conversation.