The Catholic Church's "Liberalism" began mid-19th century with the beginnings of "Christian Socialism," as an antidote to atheistic Marxism and Communism.
Christian Socialism is an international political movement that was immensely strong well into the 80s and is the parent of the EU, particularly in France, Belgium, Germany, and Italy. Politicians who ran these countries could be Christian Socialists first, and patriots second.
Many Catholic "liberal" intellectuals, began with their studies of Pius IX, whose inspiration was a church-centered socialism, inspired in turn by the early church which attempted to provide parish-based, cradle-to-the-grave care for Christians, funded by the wealthier members of the Church.
Many graduates of Catholic Colleges in the US with whom I have studied, were IMNSVHO, overly enthusiastic about Christian Socialism and the rousing encyclicals of Pius IX. It could be because their particular ancestors may not have lived in countries where the Pope, Bishop princes, and cardinal dukes maintained very harsh and repressive rule, complete with papal prisons, frequent death penalties, and a rigid caste system.
Since this is St. Patrick's Day, I'll be the first to give the Irish much credit for keeping their brand of the Catholic faith in the face of the murderous Puritan Cromwell and the later Anglican oppression ... but it's small wonder they tend to always see the Popes through green-tinted glasses. (Especially ironic, since it was the Pope that gave the English permission to take over Ireland in the first place!)
From the first paragraph:
But the evils which We then deplored have so rapidly increased that We are again compelled to address you, ... We speak of that sect of men who, under various and almost barbarous names, are called socialists, communists, or nihilists, and who, spread over all the world, and bound together by the closest ties in a wicked confederacy, ... strive to bring to a head what they have long been planning - the overthrow of all civil society whatsoever.From Paragraph #9:
But Catholic wisdom, sustained by the precepts of natural and divine law, provides with especial care for public and private tranquility in its doctrines and teachings regarding the duty of government and the distribution of the goods which are necessary for life and use. For, while the socialists would destroy the "right" of property, alleging it to be a human invention altogether opposed to the inborn equality of man, and, claiming a community of goods, argue that poverty should not be peaceably endured, and that the property and privileges of the rich may be rightly invaded, the Church, with much greater wisdom and good sense, recognizes the inequality among men, who are born with different powers of body and mind, inequality in actual possession, also, and holds that the right of property and of ownership, which springs from nature itself, must not be touched and stands inviolate. For she knows that stealing and robbery were forbidden in so special a manner by God, the Author and Defender of right, that He would not allow man even to desire what belonged to another, and that thieves and despoilers, no less than adulterers and idolaters, are shut out from the Kingdom of Heaven.There is more, but I think you can get the main idea that the Catholic Church does not approve of socialism.
Some other encyclicals that mention socialism:
Encyclical of Pope Pius XI on Reconstruction of the Social Order 15 May 1931
Encyclical of Pope Leo XIII on Capital and Labor 15 May 1891