Flipping through medieval history, religious wars were ever-present.
The most famous of these were undoubtedly the Crusades, which occurred a total of nine times over nearly two hundred years, resulting in the deaths of millions of people, followed by the Thirty Years' War that swept through the nations of Europe.
As for the religious wars in the Arab World, they were even more frequent, stretching from the seventh century all the way to modern times.
When the conflicts between different religions, or different sects within the same religion, grew too large to reconcile, one side often sought to completely purify the other physically.
With so many precedents, Li Yu was not unprepared for the war that the Silver Moon Church was about to launch.
Otherwise, he wouldn't have been nurturing Miss Rabbit all this time, even persuading her to hold on a bit longer when she hesitated about converting to Sabbath.