The cruelty of the brothers to Yosef, as well as to their father Yaakov, is appalling. However, as Professor Uriel Simon demonstrates, this story ultimately leads us to an optimistic view of the human condition.
Much of the narrative of Book of Beresis revolve around relationships within the family and in particular relationships between brothers. Through the course of the book there is a progression within the relationships. Whereas the story of Cain and Abel ends with murder, Yitzchak and Ismael come together to bury their father, Yaakov and Esav are reconciled and Yosef and his brothers each undergo dramatic changes for the better. This is all a backdrop to the idyllic relationship of the brothers who are the center of the Book of Shemot, Moshe and Aaron.
The centrality of relationships within the family throughout the book of Genesis also reflects the nature of Am Yisroel. More than we are a people we are a family.