No one can define “social justice” in any way that wins common acceptance. Advocacy of particular political goals that affect society’s resources or affect citizens rights and freedoms are often defended by recourse to our common values, the political values of Locke and our Founders, the Judeo/Christian values America was founded on. That is well and good, and provides a common ground on which to debate.
The problem with “social justice” is that it is an amorphous term which sounds as though it has an obvious meaning, but in practice it is stretched and twisted to support all kinds of social propositions, NOT to find common ground for debate, but to shut off one side of debate as being “unjust”. If one’s own side appeals to “social justice”, then any opposition is by definition “socially unjust”. So, no debate is possible.
All definitions of “social justice” I have seen are carefully crafted to reserve the appellation “just” to ideas favored by the Left, leaving “unjust” for those of the Right. As soon as I hear the phrase “social justice demands…”, I know the speaker is not seeking debate but shutting off debate. There are only two sides, his way or Satan’s way. When activists demand “the rich” deliver ever increasing money to everyone else, or the Western nations deliver unlimited billions to smaller countries as recompense for their environmental sins, the actual statement is “fork over the money or spend a richly deserved eternity in Hell”. Social Justice demands no less.