Interesting little tale.
However, the villain here was not Garibaldi.
Prior to Italy's reunification, it, like Germany of roughly the same period, was broken into a number of independent duchies, kingdoms, etc. A good part of it was under the control of the polyglot Austro-Hungarian "Empire" in the North. Most prominent of these territories were the "Papal States". This was a stretch of territory running across the middle of the Italian Peninsula and centered around the City of Rome. It was directly ruled by the Pope as a secular AND religious leader.
During the mid 1800's there was a resurgance of Nationalist
sentiment throughout most of continental Europe. Average Europeans began thinking more along the lines of Nationalist states instead of artifical political entities centered around some Feudal overlord.
Just as France, an old and established nation-state was a fulcrum of opposition to German unification, the Papal States were a fulcrum of opposition to Italian unification.
Eventually, thanks to the efforts of Garibaldi and others, the various independent Italian States were dissolved, including the Papal States, and a unified Italy constructed, under the rule of the House of Savoy, a ruling family from what is now southeastern France but which was, in actuality, Italian at the time. The French received Savoy in return for not interfering with Garibaldi and the House of Savoy in their plans for unification of Italy. This was very similar to what Bismarck achieved in Germany.
Since Garibaldi had, in the process, eliminated the existence of an independent Papal State, the Pope excommunicated Garibaldi and all those patriotic Italians who were involved in the unification of their country.
Until realtively recently, all Popes from that time on clostered themselves in voluntary "exile" within the confines of the actual territory permitted them by the Italian Government, i.e. Vatican "City".
I would also like to point out that Papal Justification of control of actual territory by the Pope was in part based on a fradulent document called "The Donation of Constantine".
This fraudullent document alleged that Constantine the Graet, as Emperor of the Romans, the First Christian Emperor, and the rightful ruler of all of the Roman Empire, had withdrawn his capitol to Constantinople, and surrendered temporal control of the western part of the Empire to the Pope as his lawful successor in all things temporal there. This claims of Papal supreamcy in the temporal realm provided the Medieval Popes with significant authority in western Europe over the temporal rulers there.
This is NOT a theological issue, any more than the Methodists et al intruding into the realm of American foreign policy and domestic constitutional issues. Like the latter, it is a good example of why a secular state is a good thing, even though a secular state can ans should acknowledge Judaeo-Christian prinicples.
Nevertheless, I applause Possenti's marksmamship and chivalry, but alas, the Catholic Church, like most mainstream western Christian faiths has been so castrated by pacifism withn the ranks that I doubt aht any individual associated with firearms will be cannonized.
Personally, I like St. Iago Matamorros myself. St. George and St. Michael are pretty good also.