Cultural relativism holds that morality is determined by one's own culture, and that no culture is superior to another. It challenges the idea of universal moral truths. However, cultural relativism is problematic as it cannot criticize objectively bad practices like genocide.
While cultures do have some differing moral codes, there is also significant agreement across cultures on basic moral rules necessary for societies to function. Many apparent disagreements are due to misunderstandings rather than true conflicts.
Ethnocentrism is the bias of judging another culture through the lens of one's own culture. It prevents open-minded understanding of other ways of life. Cultural relativism teaches tolerance of differences but not an obligation to accept all cultural practices.