The term “social justice” is one which is unfortunately polarized and even politically charged, thanks in no small part to the rise of the “Social Justice Warrior.” Though the concept has been abused both in the past and in the present, it does have a proper and even important place within Catholic social teaching as a whole to the extent that it means we are being just and merciful to the poor. Indeed, many of the abuses of social justice—by Left and Right alike—involve a distortion of one or another principle of social justice at the expense of the other principles of Catholic social and/or moral teaching. Of course, the people who suffer most when this happens are none other than the poor .
The Gospels are not a slogan, as Robert Cardinal Sarah has noted in discussing poverty, and they do not lay out a complete economic program  for us to follow. Often times attempts to eradicate poverty as such cause more harm than good, as when they promote contraception, euthanasia, or abortion (and a host of less evils). They begin with the dubious goal of eradicating poverty, but end with the more devious aim or eradicating poor people. These programs may begin with a spirit of charity, but they almost unceasingly are carried out with some spirit of arrogance.
This devolution from charity to arrogance is near inevitable, because the stated goal is itself at odds with the Gospels. As Cardinal Sarah notes, no saint sets out to eradicate poverty, for the simple reason that poverty as such is not a a great evil in the world. Indeed, it is one of the three evangelical counsels vowed by men and women religious the world over .
Poverty is a biblical value confirmed by Christ, who emphatically exclaims, “Blessed are the poor in spirit, for theirs is the Kingdom of heaven” (Mt 5:3). … The poor person is someone who knows that, by himself, he cannot live. He needs God and other people in order to be, flourish and grow. On the contrary, rich people expect nothing of anyone. They can provide for their needs without calling either on their neighbors or on God. In this sense wealth can lead to great sadness and true human loneliness or to terrible spiritual poverty. If in order to eat and care for himself, a man must turn to someone else, this necessarily results in a great enlargement of his heart. This is why the poor are closest to God and live in great solidarity with one another; they draw from this divine source the ability to be attentive to others.
The Church must not fight against poverty but, rather, wage a battle against destitution, especially material and spiritual destitution. … [so that all] might have the minimum they require in order to live….
But we do not have the right to confuse destitution and poverty, because in so doing we would seriously be going against the Gospel. Recall what Christ told us: “The poor you will have always with you …” (Jn 12:8). Those who want to eradicate poverty make the Son of God a liar.
The true evil which is so often conflated with poverty is destitution, and its spiritual equivalent, despair. Just as despair is not overcome or even really helped by its opposite error, presumption, neither is destitution helped by strictly materialistic means.
For His part, what Jesus instructs us to do in the Gospels is to love God above all else, and to then love our neighbors as ourselves (Matthew 22:36-40). Saint John the apostles instructs us that these two commandments are entertwined: “If any one says, “I love God,” and hates his brother, he is a liar; for he who does not love his brother whom he has seen, cannot love God whom he has not seen” (1 John 4:20). As an extension of this principle, any man who claims to want to love all of mankind, without loving his next door neighbor, is only fooling himself. If he cannot love his neighbor whom he sees on perhaps a daily basis, how can he claim to love mankind which perhaps nobody sees?
Contained in the Two Greatest Commandments of Christ might be the two most important principles of a truly good social justice: one which actually aims at justice tempered by mercy and driven by charity. These two principles are solidarity and subsidiarity , which balance each other. The former principle says that when one person suffers needlessly, we all suffer—and hence that if my brother suffers, I suffer, so that I am in a sense my brother’s keeper. The latter principle says that we ought not ask the state to solve problems which can be solved by the local community, nor for the local community to solve problems which can be resolved by the family.
Charity begins on a personal level, between two person, or a group of persons, for the simple reason that love in general is shared between persons. Respect and comradeship may be shared by communities, common interests by state governments. Beyond this, the federal (and to some extent state) government holds little more than power, authority, and a command of our allegiance.
The poor we will have always, but they need not always be destitute, which includes spiritual destitution. Neither are the poor truly an impersonal mass of men: living in poverty, or even living in destitution, does not deprive each person of his uniqueness nor the dignity that he shares with all other men. For our part, we do not encounter “the poor,” but rather “this poor person” or “that poor person.” It is these whom we must love and care for.
 Case in point: A loosening of morality is often promoted in the name of helping the poor, but they are often the first to be hurt by said loosening. As Prof. Budziszewski notes,
“In a country like this one, serial cohabitation and childbearing outside of marriage contribute more to poverty, dependency, and inequality than a million greedy capitalists do….Do you to really want to raise up the poor? Then…First live the Commandments. Then go among the people and preach them. Start with the ones about marriage and family….if you won’t even do so much as this, then the rest of your social justice talk is hypocritical. You may as well admit that it is all about you.”
There is a large difference between not insisting on morality as a prerequisite for the poor’s receiving aide, and dismissing morality as unimportant.
 You have to look in the Old Testament books like Leviticus and Deuteronomy to find something like that. What the Gospels do give us, in the Judgment of the Nations (Matthew 25:31-46), are the actual works of mercy which we can perform. These corporal works of mercy—and their spiritual counterparts—are what we should do for the poor and the afflicted.
 The other two are the even less worldly popular vows of chastity and obedience.
 To these might be added the principle of Universal Desintation of Goods, which is well discussed by Monsignor Charles Pope elsewhere. And the principle that social justice should not be treated as a sort of “separate justice,” that is, that it is a part of justice as such and therefore cannot be divorced from morality, etc, is also of utmost importance.