These guys are situated in pre-bronze age level of civilization. By the advent of agriculture, society was probably too structured for these sort of primitive shenanigans to hold water much without the guy or the village being obliterated by the larger tribal community. Although I'm not entirely sure.
Reading the Bible and Greek mythology, it doesn't seem to be those guys spent much thought before resorting to murderous violence. If kings stole a woman (Helen of Troy) I would suspect it might have been occurring in the common population as well.
I'm not sure where the layer of civilization started imposing social norms but these Amazon tribes are (were) definitely preceding that.
Clearly not. The story is full of civilisation imposed social norms. Fusiwe was deposed as a headman because he made bad strategic decisions and made enemies. Helena was marked as a dead women because she poisoned some children. Akawe was warned that it is not fair "to hit someone three times without taking a blow oneself". Rashawe held a speech about the good reasons to not kill Helena. Etc etc.
These are all social norms. Different in some sense from our ones, but they are definitely not without social norms.
To consider otherwise is to take a step into racist, prejudiced territory.
It is almost like savages are savages, and some other nations are more civilized.