Catholic Teaching: Not Even Moderate Socialism Acceptable

"34. Pope Pius XI further emphasized the fundamental opposition between Communism and Christianity, and made it clear that no Catholic could subscribe even to moderate Socialism. The reason is that Socialism is founded on a doctrine of human society which is bounded by time and takes no account of any objective other than that of material well-being. Since, therefore, it proposes a form of social organization which aims solely at production, it places too severe a restraint on human liberty, at the same time flouting the true notion of social authority." - Pope John XXIII, Mater et Magistra (emphasis mine)

"28 b) Love—caritas—will always prove necessary, even in the most just society. There is no ordering of the State so just that it can eliminate the need for a service of love. Whoever wants to eliminate love is preparing to eliminate man as such. There will always be suffering which cries out for consolation and help. There will always be loneliness. There will always be situations of material need where help in the form of concrete love of neighbour is indispensable.[20] The State which would provide everything, absorbing everything into itself, would ultimately become a mere bureaucracy incapable of guaranteeing the very thing which the suffering person—every person—needs: namely, loving personal concern. We do not need a State which regulates and controls everything, but a State which, in accordance with the principle of subsidiarity, generously acknowledges and supports initiatives arising from the different social forces and combines spontaneity with closeness to those in need. The Church is one of those living forces: she is alive with the love enkindled by the Spirit of Christ. This love does not simply offer people material help, but refreshment and care for their souls, something which often is even more necessary than material support. In the end, the claim that just social structures would make works of charity superfluous masks a materialist conception of man: the mistaken notion that man can live “by bread alone” (Mt 4:4; cf. Dt 8:3)—a conviction that demeans man and ultimately disregards all that is specifically human." - Papa Benedetto, Deus caritas est (emphasis mine)