Social justice, like most buzzwords, is so heavily used that we have ceased to think about what it means (if we ever did). It seems to have simply become a stamp of approval (much like “green” or “reduced calorie”)—if it’s social justice, it must be good. I, on the other hand, maintain that “social” adds the same gloss to “justice” as it does to “disease.” Please allow me to explain.
Some part of my brain gets very frightened when people use words without their meaning. Perhaps this is because it is a symptom of groupthink, or perhaps it is simply the offensiveness of ignorance proudly displayed. At bottom, though, I think the problem is that words, once detached from the ideas or things they represent, become very dangerous. They allow people to fool themselves and others into doing things they would never condone if they stopped to think about it.
Worse, I think some people do this intentionally, as a sort of marketing strategy for their ideas. If I know people won’t buy what I’m selling if I tell them what it is, I’ll borrow the reputation of some other word and add a modifier in front of it. So prunes become “dried plums” (which at least has the benefit of being technically correct), and toothfish becomes “sea bass.”

We make fun of this verbal slight-of-hand, but we seem to miss it when the object is abstract (justice, freedom) rather than concrete (plums, bass). When someone talks about “true freedom,” we feel as if we must nod, because they are saying something wise and noble. We simply don’t have as strong a conception of most abstract things as we do of most concrete things.
So let us think about the abstract notion of justice. I will offer as a definition of justice “getting the reward or punishment you deserve.” Sure, it’s the travel-size version, and I know several philosophy majors who are currently cataloging mentally all of the points which require elaboration and clarification (and, if you’ll pardon the pun, justification). This, however, will do for our purposes, and I think most of us would agree to that definition, even if we might (okay, would) have trouble agreeing on which actions deserve which outcome (and to what degree).
How does social modify this definition? I can think of two ways. First, it could mean that you get the reward or punishment everyone thinks your actions deserve. That is, it could emphasize the fact that the standards of desert are the product of agreement among a group of people. Second, it could mean that you should receive the reward or punishment appropriate to the actions of the group to which you belong.
The first alternative is somewhat redundant, as it is the functional definition of justice (i.e. how it appears in practice). So to have any meaning, it must be about altering those commonly held standards in some way—to benefit some particular people (or groups of people). It’s taking rent-seeking to a whole new level. Life becomes about spin and PR—getting people to believe your actions deserve a different outcome because they are yours. In other words, that different rules apply to you—that some animals are more equal than others.
The second alternative ends where the first does. The first says that there is a different system for different groups; the second says that, while there is a single system, your outcome depends not on your deserts, but those of the group to which you belong. So while your individual acts may deserve punishment, so long as the aggregate account of the group is in surplus, you receive reward instead.
Whereas the first offends our sense of justice only to the extent that we have smuggled egalitarianism into it, this one offends it wholly. This second alternative allows for individuals to receive what they do not deserve because someone else deserves it (and therefore, the person who deserves it more presumably receives it less). Imagine that one member of the group deserves a one-year prison sentence, and another deserves a parade. When aggregated, the group deserves a congratulatory note with a candy bar. The first is much better off; getting nothing would beat the prison sentence, so the candy bar is just gravy (not literally). But the person who deserved a parade gets a gimmicky (though tasty) congratulation. Both are unjust, or receiving what you do not deserve.
The truth is, we cannot reckon justice in aggregate terms without committing injustice. We must reckon it in individual terms. By doing so, we will also ensure justice at the group level. But if we mete justice at the group level, we will in almost all cases insure injustice at the individual. Of course, this is exactly the point Alexander Hamilton makes in Federalist 15 concerning the action of laws on states rather than individuals (and which many unwittingly echo in condemning the use of sanctions in international relations). Economic sanctions against a brutal dictator’s country generally do not harm the dictator, or harm them much less than intended, because the cost is divided among all who live in the country (and the dictator can skew that division in his favor). Those who do not share the same desert as the dictator receive it nevertheless.
Alexander Hamilton, of course, knew a great deal about social diseases as well (if John Adams is to be believed). So in his honor, let us inoculate our conception of justice against this social disease.