A few things that were once considered culturally acceptable by various groups:
- The Crusades
- Killing infants by exposure (leaving them to die)
- Murdering Jews
The list could go a lot further than that but the point is, at some point in time there were large groups of people found these things socially and morally acceptable. If you are going to take moral relativism to its ultimate end you would have to contend that all these things, even though they are detestable behaviors to us, were perfectly morally acceptable to them because what is true for us may not have been true for them. At the end of the day subjective truth fails. It is possible to be fully convinced of something and be wrong. That is easier to see in others from past decades and centuries than it is to see in ourselves.
We have our own list of things today that are viewed as socially acceptable, “our truth”, that hopefully one day people will look back on and see as barbaric practices. Abortion is #1 on that list. Can you imagine some kid 200 years from now asking his dad if Americans really did kill 45 million of their own babies (dwarfing the 11-17 million killed in the holocaust). Not just murderous, hate-filled people…but every day folks just like you and I giving permission for their babies to be killed before they were born. But if moral relativism prevails we just continue to delude ourselves into thinking bad is good and good is bad.
Culturally defined, subjective truth, just doesn’t work out in the real world. I understand why people find it so appealing but the reality is in the end it will fail to do a better job than the objective truth it set out to replace.