What differentiates morality from law, culture, or even preference?
All of the above tend to overlap a lot, but not always. I think we can all identify laws, cultures, and personal desires which are immoral. Which means morality must be separate from law and personal preferences.
We know that laws are made by man collectively, imposed by the majority/powerful. Whilst preferences are personal to each individual. Culture values bridges these two, in the sense that it is not constructed, but evolved through the collective preferences of individuals.
Values which are individual = preferences
Values which are collectively constructed = law
Values which are collectively evolved = culture
If morality had the capacity to judge all of these, moral values must be separate from all of them. If moral values are man-made, then they lack the capacity to judge either one or more of the above (because they would equate to one of the above concepts).
To put that into a working example, let’s take racism. Some individuals are racist. I think we can judge that individual’s values regarding race to be immoral. Some laws are racist. We can also judge laws which discriminate based on race to be immoral. Some cultures are racist. I think we can judge cultural values which denigrate people based on race are immoral.
But if morality is man-made, it must be relative. If morality is relative, by what standard do you judge a culture to be immoral? With relative morality, if you are able judge the racism as immoral, racists have just as much right to judge your anti-racism as immoral. Which is how morality which is man-made is self-defeating (paradoxical).