Actually I don't think it's most cultures accept it as ok, it's just that America accepts and as long as America does it everyone thinks it's ok. That's not to say that other cultures don't do it though, some do, but not most.
Also if you know it's tabu then why allow it? That's like saying stealing is ok, but we'll let people steal cause it provides a balance in the society.
Also sex doesn't make a mature game correct? A mature game is one that discuss's topics which grown ups face and shows what's right and what's wrong such as treachery and dictatorships and tyrants and corruption. Not just sex.
Also I don't oppose the fact that theirs sex, I oppose the fact that I'm forced to see it.
Of course in my culture violence and gore isn't accepted, but sex isn't accepted because of how tabu it is and how much curroption it can cause, nudity in video games has the same effect as sex outside of it; violence however doesn't since the reason violence isn't accepted is cause it results in innocent people dying and pain to the family's of those who die, in video games no such pain occurs and no souls suffer.
So CDPR shouldn't waste time adding a line of code to censor a 3d model but they should waste time modelling it and animating the humping and record the orgasms and programming it into the game? It's part of the world sure, but did you have to show it? Why not just blur it or do like bioware? So adding what's wrong is not a waste of time while not doing so isn't?
Also why not apply that "small group and big group" talk in the real world first, I mean you already allow gays and transgenders and what not now, imagine what they will ask for later.
Additionally we are not a small group demanding for something random, we are asking protection from what is wrong, something that quite frankly everyone should be asking for, and you'll see; one day sex will be socially accepted and your (grand)grandchildren will suffer from it.
Also being able to "withstand" nudity has nothing to do with maturity.