The term “social justice” is like “deprivation” and “progressive” – distorted, hijacked terms used to further some squalid Leftie agenda that cannot exist without a nice term to shield it from the sunlight.

“social” in the second context is the mob, the majority, the squeaky wheels and ax-grinders. Hence, damnable.

So what exactly does social justice mean? Rawls seems to make a statement that runs counter to the idea that social justice involves restricting individual rights for the good of society: “Each person possesses an inviolability founded on justice that even the welfare of society as a whole cannot override. For this reason justice denies that the loss of freedom for some is made right by a greater good shared by others.” (From Wikipedia.)

And yet when it is used in political discourse “social justice” usually involves minimum wages, redistribution of wealth and strongly progressive taxation. What does it mean?

You are conflating Welfare with Social Justice/Social Rights. Social Justice is built upon Social Rights, btw, so once JS Mill kicks Social Rights away, Social Justice has no foundation.

Mill doesn’t really discuss “social justice”; the phrase doesn’t appear in On Liberty. In fact he argues, in the beginning of chapter 5, that the argument for free markets rests on a different foundation from the argument for individual liberty, and that in principle society may regulate the economy:

This is the so-called doctrine of Free Trade, which rests on grounds different from, though equally solid with, the principle of individual liberty asserted in this Essay. Restrictions on trade, or on production for purposes of trade, are indeed restraints; and all restraint, quâ restraint, is an evil: but the restraints in question affect only that part of conduct which society is competent to restrain, and are wrong solely because they do not really produce the results which it is desired to produce by them.

(The above argument is actually one area in which I disagree with Mill – individual liberty does have an impact on whether certain regulations of the economy are right in principle, as Johan Norberg has argued.)

In other writings such as Principles of Political Economy (1848) Mill does go into more detail on economics, and there he does concern himself with economics and equity. For example, he wrote: “I conceive it to be highly desirable, that the certainty of subsistence should be held out by law to the destitute able-bodied…. Since the state must necessarily provide subsistence for the criminal poor while undergoing punishment, not to do the same for the poor who have not offended is to give a premium on crime.” (Chapter XI, §13.)

However, the general thrust of his thought seems to be that it would be better to reform capitalism (for example by taxing inheritance punitively and “life incomes” less) than to opt for socialism – not least because socialism would threat the individuality and diversity that he so treasures.

Sorry for the length of the comment, but Mill is fascinating and I easily get carried away

Thing is, if they heeded that, then they would be at odds with their party.