"moral theology flows from catholic social justice theory - not the other way around and moral theology does not come first."

Citation needed.

Moral theology is based on applying systematic theology to what man has to do to achieve ultimate beatitude. Social justice is part of that as it is part of the virtue of justice as it specifically applies to distributive justice, but all that is a subcategory of moral theology. To claim moral theology flows from catholic social justice theory is like saying the earth sciences flow from geophysics.

I think what is going on is that "Social Justice Catholics" are often accused of moral relativism. This is because they often come to the same conclusions as moral relativists. But the charge of relativism is false, as the reason why they come to those conclusions is because they are over emphasizing a small slice of Catholic teaching to the point it eclipses other de fide teaching.