Rationality from whose vantage point? Is it rational to execute prisoners? Some say yes, others say no. They make arguments predicated on assumptions that seem reasonable to them…but not to others. And the arguments come from both the sky-hooks and from actual experiences. The issue never gets resolved however because we have no moral font to turn to that can assemble the precise premises needed to construct a conclusion that is unassailable.
All of moral agendas are based on subjective points of view. That is why circumstances can change to alter them. This doesn’t resolve the issue, of course, but we can only relate and react to it from the manner in which we actually experience it.
The “only thing”?! That’s sufficient to make the world go around. And that’s sufficient to keep people flip-flopping from one point of view to another. The illusion the must be avoided is that in changing our minds we are making “progress” toward a moral position that is the optimal one.
But that’s the way the world works. You think this. Something happens. You think something else. In one context this point of view makes sense, in another it does not.
I think of moral codes as social strategies. From that perspective then some degree of optimization can be approached - reflected in the stability of the societies that people operating on these ‘moral-programs’ create.
For example the ‘turn the cheek’ varient really does outdo ‘eye for an eye’ in creating large stable societies for example - in both real life and simulations.
You say the situation is fluid because ‘morality is based on context’ and that is to some extent true, however, it must not be forgotten that there is one constant involved within all contexts where morals are applied - the presence of humanity itself.