Another heretical idea from Vatican II that also relates to Ecunemism is the civil right for religious liberty, which clearly would undermine the need for evangelization and the spread of false religions and doctrines, even if they are opposed to the Catholic teaching .
From Vatican II:
"The Council further declares that the right to religious freedom has its foundation in the very dignity of the human person... This right to religious freedom is to be recognised in the constitutional law whereby society is governed. Thus it is to become a civil right."2 (Declaration on Religious Liberty Dignitatis Humanae, paragraph 2)
This contradicts the words of Pope Pius IX's in Quanta Cura (1864):
"And from this wholly false idea of social organisation they do not fear to foster that erroneous opinion, especially fatal to the Catholic Church and the salvation of souls, called by our predecessor, Gregory XVI, insanity, namely that the liberty of conscience and worship is the proper right of every man, and should be proclaimed by law in every correctly established society... Each and every doctrine individually mentioned in this letter, by Our Apostolic authority We reject, proscribe and condemn; and We wish and command that they be considered as absolutely rejected by all the sons of the Church."