Here I briefly describe why I think some people think moral relativism has a significant truth value and why their intuitions are wrong.
What does moral relativism say? “You can’t say one culture’s values are better than another because you evaluate them through your own biased lens.” I hope this is a fair synopsis.
Counter: Moral relativism is incoherent because utility is grounded in the real world, and different actions certainly have different effects on the real world. I bet this is clear to most moral relativists, but I believe there exists a line of reasoning which obscures their thinking.
Moral relativists are probably seeking tolerance. People used to be stoned or burned at the stake for believing something heretical outside of the Overton window. For most of us that have discovered the fruits of living in a liberal, diverse society, we obviously do not want to live in a society where people with “wrong” honest opinions are true are too afraid to speak their mind in the market of ideas.
Moral relativists are also probably against imperialism. A big justifier of imperialism was that the colonized beliefs were wrong and they needed to be managed.
Moral relativists want to prevent stonings, the closure of public discourse, and imperialism, but instead of focusing on how one ought to respond to another person or culture’s wrong belief, they say the belief isn’t wrong in the first place. The threat of the slippery slope that starts at the judgment of another culture’s values is perceived by moral relativists as worse than not acting as if cultural beliefs did have different utility.
Followed to its conclusions, this creates an unmanageable world to live in as we simply cannot maximize utility functions that are grounded at all in the real world.