This, from Catholicism 101, says it all:
"A Catholic monk who heard ex-Communist Bella Dodd speak at Fordham University in the 1950s had this to say:
I listened to that woman for four hours and she had my hair standing on end. Everything she said has been fulfilled to the letter. You would think she was the world’s greatest prophet, but she was no prophet. She was merely exposing the step-by-step battle plan of Communist subversion of the Catholic Church. She explained that of all the world’s religions, the Catholic Church was the only one feared by the Communists, for it was its only effective opponent.
The whole idea was to destroy, not the institution of the Church, but rather the Faith of the people, and even use the institution of the Church, if possible, to destroy the Faith through the promotion of a pseudo-religion: something that resembled Catholicism but was not the real thing.
Once the Faith was destroyed, she explained that there would be a guilt complex introduced into the Church…. to label the ‘Church of the past’ as being oppressive, authoritarian, full of prejudices, arrogant in claiming to be the sole possessor of truth, and responsible for the divisions of religious bodies throughout the centuries. This would be necessary in order to shame Church leaders into an ‘openness to the world,’ and to a more flexible attitude toward all religions and philosophies. The Communists would then exploit this openness in order to undermine the Church.
In the human element of our Church, we are seeing the results of this infiltration coupled with the effects of the pressures of secular materialism and sheer hedonism in the popular culture."
You see, there IS only ONE truth. And it does not change, and the gates of Hell shall not prevail against it.