could you explain me, why moral relativism entails the notion, that moral "should be" relative ? Is it not a metaethical view ? (How it "is", and not how it "should" be)
There are the consequentialist ethics : preference utilitarianism, hedonist utilitarianism, negative utilitarianism, lexical utilitarianism. And there are also a lot a deontological ethics, by example the kant’s categorical imperative.
but you don`t have a way to prove this. Moral relativism is quite simple to prove. Doesn`t show that moral relativism is true, because we can show, that different cultures show different moral notions.
Let's define culture: Handed down rituals and expressions (like food, clothing, music, religion) that bind a community. Morality: Values and choices about right and wrong behavior.
Morality is often taught through culture but can be treated as independent, even spanning cultures.