Some societies may look as if they go in for weird immoral behaviour, different from our own, but there seem to be a few fundamental core values like “Murder is wrong” that are always followed. A tribe may burn widows and sacrifice children in the belief that this is for the ultimate long-term heavenly good of the victims involved, but they don’t sanction the murder of widows and children as such. Absolutists say that Relativists only look at what people do, not at what they actually believe.
Also, The Existence Of A Wide Variety Of Moral Beliefs Doesn’t Prove That All Moral Beliefs Are Equally Valid. Different People Once Held Very Different Beliefs About The Shape Of The Earth. Not All These Beliefs Were “Valid” — Only One Set Of “Round Earthers” Actually Knew The Truth. Donut-shaped earth north hole
Absolutists say that human morality is like this – there is real “moral knowledge”. Some moral beliefs are “true” and some aren’t, it’s just that we haven’t figured out how to prove which is which yet.