I agree. Morality is subjective, but justice, its transitive corollary, is not. An observer may not be able to accurately judge the moral value of someone’s personal actions, but their treatment of others is observable and subject to evaluation.
As to the moral executive function being the fundamental one, I honestly cannot see how this can be gainsaid. Everything we choose to do or not do is fundamental to everything else. Other executive functions are either subordinate or hyponymic to this one. The will, a simple (binary), executive function is but a switch controlled by the moral (choosing) function. One does or one does not. We also chose the parameters (focus, direction) of our attention, a complex executive function.
Our choices are always based on our values within a given context, of course. Values are the conceptual element that complete the composition of the moral function. We develop preferences based on the values we learn through the application of our attention. We then execute the results of our assessment through our will.