35 The wisdom and supreme utility of this doctrine are admitted by all who really understand it. With good reason outstanding statesmen have asserted that, after a study of various social systems, they have found nothing sounder than the principles expounded in the Encyclicals Rerum Novarum and Quadragesimo Anno . In non-Catholic, even in non-Christian countries, men recognize the great value to society of the social doctrine of the Church. Thus, scarcely a month ago, an eminent political figure of the Far East, a non-Christian, did not hesitate to affirm publicly that the Church, with her doctrine of peace and Christian brotherhood, is rendering a signal contribution to the difficult task of establishing and maintaining peace among the nations. Finally, We know from reliable information that flows into this Center of Christendom from all parts of the world, that the Communists themselves, where they are not utterly depraved, recognize the superiority of the social doctrine of the Church, when once explained to them, over the doctrines of their leaders and their teachers. Only those blinded by passion and hatred close their eyes to the light of truth and obstinately struggle against it.
Source: Divini Redemptoris (Vatican.va)