But I also think, as a scientific naturalist, that the idea that the universe contains any inherent ethical values is nonsense. The universe is morally indifferent and the very idea of morality is dependant of humans (or other conscious entities) beliefs and judgements. In this sense, morality is subjective.
I quite agree however the central issue on subjectivity here is different, that of the opinion/fact kind, as to whether therefore moral views are just and only opinions, the above form of subjectivism does not necessarily and exclusively lead to opinion based subjectivism, that is another hasty generalisation and/or equivocation over subjective (just highlight the issues, other arguments of yours might not be committing these fallacies although my reading of your other comments does indicate these are the fallacies you are commiting).
As I argue above, I think there are constraints and shaping factors that yield remarkably similar and consistent moral schemes across time and culture, which is why I’m not a strict cultural relativist, but ultimately something is only moral or immoral because we decide it is so, howevere this decision is made.
So there are common structures the lead to how decisions are made (“opinion-makers”?) but “ultimately” it is only because we decide it is so, regardless? This is confused. With such biological and cultural opinion-makers (or constraints and factors) opinions should be predictable in the provisional, probabilistic and population sense, such that changing the opinion-makers should have reasonably predictable effects on the resultant opinions. You do not seem to be able to have your cake and eat it… On what basis, apart from here appearing arbitrary, do you justify your “ultimately” assertion?