If a philosopher managed to prove, beyond the shadow of a doubt, that morality is an arbitrary, relative human construct, next to nothing would change in our day-to-day lives. Sure, it might cause a stir amongst academics, but no laws would change. Society would not be disrupted and few (if any) people would change the way they think, speak, and act. The same would be true if a philosopher proved that morality was a fixed, universal truth; this information would not affect the average person in the slightest. But why not? Simply put, knowing whether morality is relative or absolute does not change the fact that we must, to an extent, accept and follow our society’s definition of morality. On an individual level, moral norms must be followed so that people fit in and can function properly. On a societal level, we need moral norms to maintain a sense of trust and community, where each person knows what is morally expected from them. Whether morality is relative or absolute, it does not change the fact that we need to strive for it.
This argument prioritizes mindless groupthink over rational, individual moralizing. Sure, it may seem beneficial to adhere to your society’s idea of morality, but what if that society is corrupt? In many instances, from the Civil War to Nazi Germany, it is better to rebel against the norm than follow it for the sake of ease and unity.