Mindless relativism? That's just how things are, plain and simple.
You're going off wrong about this. Humans are just one variable, you're reducing it to that and that's not how it works. Yes, there have been rare cases of people who were raised with no human contact, but I'm speaking from an existential/total standpoint. Of course you could just blip every single person out of existence except you and some Victoria's Secret supermodel, but you will still exist within a dualistic framework. You'd very much understand good and bad. You wouldn't put your hand in the fire, jump down from a very tall tree, eat dirt, stop breathing or sleeping, etc. The point I'm trying to make is it cannot be like this for some things and not for others. It has to apply to everything. You can't just have a 100% Aryan Chad/Stacy population even if you went full genocide and then killed every sub-8 human alive and to be born. Chad and Stacy wouldn't always pop out other Chads and Stacies. It's just basically impossible no matter how you paint it.