Maybe the misunderstanding here is that Irish_Farmer thinks that accepting the fact that morals are relative to a culture means embracing their morality ?
Finding that cultures throughout time and space have different sets of rules does not show that these rules are all good. It just shows that there is not a general set of rules that is accepted as true everywhere and at every time (though laws against killing family members and incest are common to most civilizations).

I think most people would like to have absolute morals (obviously meaning _their_ morals) but that often there is no rational basis for condemning certain behaviors.