Last month the Independent Journal Review published an article by Kyle Becker as he profiles the men whom he believes to be "founding fathers" of the left. His list goes all the way back to Plato. I frankly was a bit surprised to see Sir Thomas More included in that list. If in fact More did espouse the abolition of private property, that in no way diminishes his witness to the sanctity of marriage and the primacy of the papacy. In their defense, he was a martyr for the faith and thus is properly recognized as St. Thomas More.
Many of the others were no surprise: Marx, Dewey, Marcuse, etc. Quite a few were unknown to me. I'd suggest a study of these, to see how thinking inimical to Christianity was promulgated throughout the centuries.