Answer :
This question is incomplete. Here's the complete question.
Watch The Origin of Race in the USA (PBS)
Why might a society aim to justify existing social norms with faulty science?
Answer:
Social norms are part of the social structure and are associated with political, economical, and scientific ideas of the time.
Science might seem as inherently objective, however, it´s also a human development influenced by the ideas of the time.
Explanation:
For example, the expansion of the slavery system brought many theories, today recognized as faulty science, that justified slavery by correlating physical features, behaviors, and legal rights, and magnifying the differences between races, especially between blacks and whites, in agreement with the idea of slaves not being considered as humans.