I'm not sure I understand what you're trying to say with choosing to like something over another or the idea of a choice not being true.

Morality can only be defined in relation to a certain set of values. You could do any action and if is in accordance with your values then it is moral by definition.

I also dont understand your second paragraph and your reference to legal systems and principle.

I do not think psychology or social factors are irrelevent to ethics but that for the purpose of my specific argument I think construing it as a model is more relevent. I am assuming here that we have values as just a product of our being, regardless of the particulars of how they arise, which is where I believe those factors would be more relevent.

To express the paragraph you quoted with some more context: I think that there is no such things as "values" outside of the experience we value. When we say "I prefer the taste of orange juice to apple juice", I think that can be translated to "I prefer an experience involving the taste of organge juice to apple juice".

There are infinite hypothetical experiences and we arrange these into hierrachies, aka we value them in relation to eachother. To state again, this isnt a psychological statement about how people view morality but a way of construing a basic idea that we have preferences for different experiences.