Here is how I learned it. Once upon a time in the West, the Church aimed to save all of society by bringing everyone under the umbrella of the Truth. The shattering of Western Christendom with the Reformation caused a problem. If the Catholics were right, then the Protestants were damned, and if the Protestants were right, the Catholics were damned. You know all about the “Wars of Religion,” which occupied Europe in the 16th and 17th centuries.
Ultimately this led to the Westphalian system and a gradual acceptance that there would no longer be One True Religion in the West. Monarchs who even took a skeptical view on religion, such as Frederick the Great, arose in the 18th century. In this case, you had a Calvinist Hohenzollern dynasty which could not bring its Lutheran populace on board. In Saxony, you eventually had Catholic dukes ruling over a Protestant populace.
But another aspect of the collapse of universal Christianity in the West was the emergence of radical Protestant groups which understood most of society to be damned and beyond redemption. The separatism of the Amish is an extreme case of this. They don’t even attempt to convert anyone to their religion, which has turned into an ethnicity. This withdrawal of radical Protestants from attempting to force the temporal world to their will has expressed itself most fully in the United States of America, which never had a state-supported religion on the federal level, a radical innovation in its day.
This strain of Christianity is suspicious of the state and society in part because of the suppression their beliefs and practices by both the state and society in which they first emerged. But their relegation of the majority to the ranks of the damned also allows for a modus vivendi in this life. As a contrast, see this apologia for the Pope Pius IX behavior in the Mortara case in First Things, Non Possumus.
The basic argument seems to be that the Pope was motivated by the salvation which was being offered to the soul of the child baptized by the family’s maid. The curious thing is that the whole time I was reading the piece I was thinking about Islamists who would argue that coercive conversion of children of other religions to Islam is still good on the balance because they are now Muslims. The general way this wors is somehow a child is tricked into saying the shahada, and Islam enjoins that once converted one can not apostatize (the Kafir Kalash of Pakistan are suspicious of their children being around their Muslim neighbors because this has happened many times in the past to them).
Some of the same extreme “compassion” seems to be cropping up in American politics, as a deviation from the Truth is no longer tolerated. Pius IX was out of step with his time, as secular liberalism was on the rise. Today I wonder if that liberal in its own turn may have to give ground to a new totalitarianism.