Pius XII: "Disturbances, riots and revolts are organized and fomented" by Atheism, when Religion is taken away.

That which seems to Us not only the greatest evil but the root of all evil is this: often the lie is substituted for the truth, and is then used as an instrument of dispute. On the part of not a few religion is passed by as a thing of no importance, and elsewhere absolutely prohibited in family and social life as a remnant of ancient superstitions; public and private atheism is exalted in such a way that God and His law are being abolished, and morals no longer have any foundation. The Press also too often vulgarly reviles religious feeling, while it does not hesitate to spread the most shameful obscenities, agitating and with incalculable harm leading into vice tender childhood and betrayed youth.

By means of false promises a people is deceived and provoked to hatred, rivalry and rebellion, especially when the hereditary faith, the only relief in this earthly exile, is successfully torn from its heart. Disturbances, riots and revolts are organized and fomented in continuing series, which prepare for the ruin of the economy and cause irreparable harm to the common good.

We must above all deplore with overwhelming sadness that in not a few nations the rights of God, Church and human nature itself are outraged and trampled upon. Sacred ministers, even those invested with high dignities, are either driven from their proper Sees, exiled and imprisoned, or impeded in a manner preventing them from exercising their ministry. ...

Since these innumerable evils spring, as We have said, from one source only, the repudiation of God and contempt for His law, it is necessary, Venerable Brethren, to offer to God fervent prayers and recall all to those principles whence alone can come enlightenment for minds, peace and concord for souls and well ordered justice between the various social classes.

As you know, once religion is taken away there cannot be a well ordered, well regulated society.

Pius XII
Anni Sacri (On a Program for Combatting Atheistic Propaganda)
March 12, 1950