"Essentially good people are capable of evil", to what extent is this statement accurate within the novel?

The Secret River examines how the harsh British class system of the 18th and 19th centuries condemned people like William to a life of crime. Grenville exposes the harsh choices that people of William's class faced in order to survive. It was not a question of good or bad but of starvation or theft. In her chronicle of William's life in London, Grenville wants the reader to understand that the convicts who first settled modern Australia were not bad, just desperate. Australia has chaffed under its moniker as a land of convicts since its inception. Grenville's empathetic account of William's life represents an attempt to embrace Australia's convict past and give it a human face.