How does the Giver shock Jonas when they are talking about the community's scientists?

In chapter 13, the Giver tells Jonas what happened to the community when the last Receiver of Memory was released. The Giver explains to Jonas that the community erupted into chaos because the citizens could not process or cope with the difficult memories and emotions that were released. When Jonas questions the Giver regarding where he stores the memories, the Giver tells Jonas that they are in his being. Jonas proceeds to inform the Giver that his science and technology instructors have taught him how the brain works and can elaborate on how the human brain functions. The Giver bitterly responds by telling Jonas, "They know nothing" (Lowry, 105). Jonas is shocked at the Giver's accusation, and it is the first time Jonas has witnessed the Giver speak rudely during their sessions. The Giver proceeds to explain to Jonas that his instructors understand the functions of the brain but lack wisdom and necessary knowledge to implement their understanding. Without knowledge of the past, the instructors are completely ignorant of how to properly implement their findings.