It's just moral relativism. While not usually the most popular of philosophical schools of though, it's hardly new, either. https://plato.stanford.edu/entries/moral-relativism/

But, fine, let us suppose that morality is objective --- we can even go so far as to say that it is entirely so, and not at all a moving target. That doesn't necessarily mean that your moral compass, or even the compass of society at any given time, is correct --- even if you strongly feel that it should be. Ethics involves the careful and systematic study and consideration of morality. Words like "obvious" don't really have a place in ethics.