41 Lastly, there remain those who, while they do not approve the separation of Church and State, think nevertheless that the Church ought to adapt herself to the times and conform to what is required by the modern system of government. Such an opinion is sound, if it is to be understood of some equitable adjustment consistent with truth and justice; in so far, namely, that the Church, in the hope of some great good, may show herself indulgent, and may conform to the times in so far as her sacred office permits. But it is not so in regard to practices and doctrines which a perversion of morals and a warped judgment have unlawfully introduced. Religion, truth, and justice must ever be maintained; and, as God has intrusted these great and sacred matters to her office as to dissemble in regard to what is false or unjust, or to connive at what is hurtful to religion.
Source: Libertas (Vatican.va)