Aaron understood precisely where the people of the city of Jerusalem differed from what he knew Jehovah wanted them to understand. They had said that Jehovah would save everyone, and that statement clearly indicated that they rejected the coming Messiah. Nevertheless, Aaron asks to have them commit to their belief.
When Aaron asks if they believe that the Son of God would come to redeem mankind, they respond that Aaron could not know that, since it was in the future. Those things promised in the far distant future did not seem real to them. Thus, this Jerusalem expelled a prophet teaching about the coming Messiah, even as the Old World Jerusalem had expelled Lehi, a prophet teaching about the coming Messiah.