Why is the Song of the Family so fierce upon Kino and Juana’s return to La Paz?

Steinbeck constructs Kino's return to La Paz as an event that brings Kino back to the family-centered ideals with which he began the story, but his recollection of the Song of the Family has a significant undercurrent of defiance and anger. His family has been destroyed, yet he clings to that ideal, for it is all that remains for him.