116 Yet let no one think that all the socialist groups or factions that are not communist have, without exception, recovered their senses to this extent either in fact or in name. For the most part they do not reject the class struggle or the abolition of ownership, but only in some degree modify them. Now if these false principles are modified and to some extent erased from the program, the question arises, or rather is raised without warrant by some, whether the principles of Christian truth cannot perhaps be also modified to some degree and be tempered so as to meet Socialism half-way and, as it were, by a middle course, come to agreement with it. There are some allured by the foolish hope that socialists in this way will be drawn to us. A vain hope! Those who want to be apostles among socialists ought to profess Christian truth whole and entire, openly and sincerely, and not connive at error in any way. If they truly wish to be heralds of the Gospel, let them above all strive to show to socialists that socialist claims, so far as they are just, are far more strongly supported by the principles of Christian faith and much more effectively promoted through the power of Christian charity.
Source: Quadragesimo Anno (Vatican.va)