Am I right in refusing the lecturer's invitation to marry off my eight-year-old daughter, following the example of the Mother of Believers, Aisha?

What the lecturer mentioned regarding the permissibility of early marriage is correct and firmly established by the Quran, Sunnah, scholarly consensus (Ijma'), and the practice of the Companions, as well as what Muslims have traditionally followed. In the Quran, the verses of "Al-Talaq" (Divorce) and "Al-Nisa" (Women) indicate the permissibility of marrying young girls and orphans. In the Sunnah, there is the marriage of the Prophet, peace and blessings be upon him, to Aisha when she was six years old, and consummating the marriage when she was nine years old. Scholars have unanimously agreed on the permissibility of a father marrying his virgin young daughter to a suitable match. The Companions also applied this, such as the marriage of Umar ibn Al-Khattab to Umm Kulthum bint Ali when she was young, and Al-Zubayr marrying his daughter when she was a newborn. Delaying marriage is an innovated practice that goes against what Muslims have traditionally followed, and it has negative consequences such as the spread of indecency and a decrease in progeny.