Final answer:
Jefferson's ideas about Native Americans and African Americans are wrong due to his racial prejudices and the neglect of the cultural and intellectual capacities of these groups, which conflicted with the Enlightenment values he otherwise advocated.
Step-by-step explanation:
In "Jefferson's Ardor", the argument posits that Thomas Jefferson's ideas about Native Americans and African Americans are wrong primarily because they reflect deeply seated racial prejudices and misconceptions about the capabilities and cultures of these groups. Jefferson's policies and views neglected the fact that many Native American societies were already sophisticated agriculturalists and that African Americans possessed equal capacities to whites, thereby contradicting the Enlightenment principles of natural rights that he famously espoused in the Declaration of Independence.
Furthermore, despite acknowledging the immorality of slavery, Jefferson failed to act consistently with these convictions. He envisioned an America primarily for White farmers, suspecting that full emancipation of African Americans would lead to race wars and chaos, underpinned by pseudo-scientific beliefs of African inferiority and fearing the consequences of integrating former slaves into society. His policy towards Native Americans also aimed towards eventual assimilation and the appropriation of their lands to serve white expansionist interests.