Dragon’s hatred of the nobles does not seem to include Sabo. In fact, Dragon was shocked to hear the boy’s shame of being born a noble, and listened to what he had to say. Following the boy’s confession to the plot, Dragon and the Revolutionary Army rescued the citizens of the Gray Terminal. He later saved Sabo’s life after the latter’s boat was shot and burned down by a World Noble.
Because Sabo lost his memories of Luffy and Ace after this incident, Dragon was not aware that Sabo was a sworn brother to his son while Sabo was unaware of Dragon being Luffy’s father. When Sabo refused to return to his family, Dragon allowed him to join the Revolutionary Army. Dragon personally trained him, enabling him to rise through the ranks until he became the Revolutionary Army’s chief of staff.
However, due to Sabo regaining his memories during the aftermath of the Marineford War, Dragon was made aware of the relationship between Sabo and his son. In return, Sabo was made aware that Dragon was Luffy’s father.
Sabo refers to Dragon as “Dragon-san” and appears to be loyal to him and is trusted enough to lead the Revolutionary Army’s investigation of Dressrosa’s weapons trade. He also granted Sabo permission to obtain and consume Ace’s Mera Mera no Mi.
Even after regaining his memories, Sabo did not leave the Revolutionaries to resume his dream of being a free-sailing pirate, showing a firm conviction to Dragon’s cause.