Thoughts on Fiction

if you presume that all morality is subjective, then that eliminates a profound amount of tension in many kinds of stories.

I think moral judgements involve both subjective and objective factors. "Objective morality vs. subjective morality" is a false dichotomy to begin with.

So, I've been reading about moral philosophy and I've found some people who seem to reject the objective vs. subjective dichotomy. The ones I really like are Iris Murdoch and Philippa Foot. Their view of morality is like this: Morality is our term for the rational pursuit of happiness, in accordance with the particulars of psychology. As a human being, this is what you're constructed to do. You have no choice about your moral nature, only whether you perform it well or poorly. Human opinion does not determine moral principles, but human psychology does.

"You have no choice about your moral nature, only whether you perform it well or poorly."
The problem with debates about morality is the that the term "morality" is being used to describe a vast range of factors and conflicting interests.
Your statement's meaning is ambiguous to the point where it could be saying too many different things.
I know that I've changed my moral position on a number of issues during my life. As you become more informed and more wise, your moral compass will shift.
One could argue that your moral nature is independent of how much you know, but you could just as well define moral nature as that which emerges in a way entirely dependent on what you know. A child with little life experience is not held to the same standard of morality as an adult.

Moral philosophy is the project of generalizing approaches to decision making with the purpose of maximizing the chances of optimal outcomes. It is a system of measuring the desirability of actions in the same way that the metric system is a tool for measuring physical properties. It is essentially a practical tool for everyday decision making. The problem arises when these guiding principles (generalizations) start to be viewed as having some innate value, as if they are cosmic rules that exist outside of human opinion. They do not. They exist because they are helpful and practical. That is all morals are.

It's possible to use rhetoric to justify any moral stance. Internal consistency is used as a standard for judging the validity of a moral position.
The "rational pursuit of happiness" sounds like a baseline value, but everyone's idea of what makes them happy is so varied that I wonder if it's really useful.

I've come to conclude that moral principles are, in fact, entirely explained as nothing more and nothing less than opinions. We decide what we want to call good and bad. We then use rhetoric to justify these opinions because we are taught to discount personal opinion as a sufficient basis for judgment.
It would be better to be honest and own up to the idea that people hold their opinions with high regard. The act of voting in a democratic election is driven by opinion. We accord opinion with the highest value when it comes to politics. Supreme court decisions are opinions.

Opinions can change. Philosophy exists to serve our opinions, not the other way around. Our opinions are primary.

It becomes a complex exercise because it quickly becomes meta. We hold the opinion that we want rational ideas of fairness to guide our moral decisions. But that desire for rationality is itself an opinion.