Your first problem was thinking that simply living is the grand scheme of things.
Synthesize the problem to its absolute foundation- culture.
Humans labor under the assumption that somehow the culmination of a way of life can be quantified and generalized, to suit the ideological bases of the assumed traditional culture. There is no stagnation to living,the problems that arise, the mentalities that are molded, and to the hope that the universe has an all-encompassing answer to why we exist. Because of this, culture cannot be theorized as something that classifies people-perhaps some of their acts of living,but never in their entirety. Humanity and its habitat is too vast and hybrid to ever fit into a singular concept or idea.
The justification for misdeeds, questionable acts of moral ambiguity, and occurrences that deviate from the fabricated mandates that govern what is civilized cannot simply be explained away as “This is my culture”.
Forget culture relativism and/or ethnocentricism. There is no room to justify gross human rights violations under the flimsy falsehood of culture, even those with deeply-rooted traditions passed through generations under a group of people with tribal identities and mentalities.
Heinous acts are singularly and irrevocably yours too answer for. And should the notion of culture arise again, recognize that as times progress and the world changes,so do the people, and it is up to each individual to evolve accordingly, or be left to an old-age mirage that has no place in this hybrid world.