If any form of moral absolutism were true, this would establish moral principles as, essentially, natural laws. Any particular set of ethical principles would be physically impossible to deviate from. As follows, every society would have no choice but to adhere to them. The fact that there's a diversity in normative systems negates moral absolutism.

Moral absolutism, ultimately, justifies ethnocentrism and inflexible conservatism. If one believes that there is one morally correct way to conduct oneself, one will be unreceptive to new ideas in regards to morality. Moral absolutism is inherently dogmatic, and therefore, maladaptive.

The fact of the matter is that morality is subjective. It's a matter of socialization, not objectively moral principles