There have been a number of societies which normally - and not just in case of famine and starvation - practiced cannibalism for food, and others which practiced ritual forms of cannibalism. But probably not nearly as many as is popularly imagined.
I am not certain that Christian Europeans needed to accuse the societies they encountered elsewhere of cannibalism and other atrocities to justify invading and conquering them.
Early renaissance conquerors had a medieval view of life, and believed that non Christians worshipped false gods, and thus devils, and thus were devil worshippers, and thus were evil, regardlessof how advance and civilized or primitive their technology was, or of how gentle or cruel their practices were.
Christian conquerors claimed that if they forced non Christian people to convert to Christianity they would be saving their souls and the souls of their descendants, and that whatever price the Christian conquerors charged for such a great service, even sometimes enslavement, was cheap compared to the benefit they brought.
In the 19th century when European societies became far more technologically and scientifically and industrially advanced than even the most advanced and ancient non European civilizations, and when European societies became more humanitarian than many non European societies - though still quite brutal compared to present day societies, to say nothing of hypothetical humane future societies - the Europeans stressed more and more the backwardness of other societies and their cruel customs as justifications for conquering them.
Other cases that shocked me include the killing and eating of Johan de Witt by a mob and the torture of György Dózsa.
According to Cassius Dio in his Roman History, Book 59, Section 29:
For Chaerea and Sabinus, pained as they were by the disgraceful proceedings, nevertheless restrained themselves for five days. 6 But when Gaius himself wished to dance and act a tragedy and for this purpose announced three more days of the entertainment, the followers of Chaerea could endure it no longer, but waiting merely till he went out of the theatre to see the boys of exalted birth whom he had summoned from Greece and Ionia ostensibly to sing the hymn composed in his honour, they intercepted him in a narrow passage and killed him. 7 When he had fallen, none of the men present kept hands off him, but all fell to stabbing him savagely, even though he was dead; and some even tasted of his flesh. His wife and daughter were also promptly slain
So Cassius Dio wrote that some of the flesh of Gaius Caesar Augustus Germanicus, nicknamed caligula, was eaten by his slayers.
Walter VI, Count of Brienne, and exiled Duke of Athens, became Lord of Florence for a few months in 1342 to 43 but was driven out by a revolution.
According to Niccolo Machiavelli, History of Florence and the Affairs of Italy, book II, Chapter VIII:
Many had come to Florence in defense of the people; among whom were a party from Sienna, with six ambassadors, men of high consideration in their own country. These endeavored to bring the people and the duke to terms; but the former refused to listen to any whatever, unless Guglielmo da Scesi and his son, with Cerrettieri Bisdomini, were first given up to them. The duke would not consent to this; but being threatened by those who were shut up with him, he was forced to comply. The rage of men is certainly always found greater, and their revenge more furious upon the recovery of liberty, than when it has only been defended. Guglielmo and his son were placed among the thousands of their enemies, and the latter was not yet eighteen years old; neither his beauty, his innocence, nor his youth, could save him from the fury of the multitude; but both were instantly slain. Those who could not wound them while alive, wounded them after they were dead; and not satisfied with tearing them to pieces, they hewed their bodies with swords, tore them with their hands, and even with their teeth. And that every sense might be satiated with vengeance, having first heard their moans, seen their wounds, and touched their lacerated bodies, they wished even the stomach to be satisfied, that having glutted the external senses, the one within might also have its share. This rabid fury, however hurtful to the father and son, was favorable to Cerrettieri; for the multitude, wearied with their cruelty toward the former, quite forgot him, so that he, not being asked for, remained in the palace, and during night was conveyed safely away by his friends.
So this makes three cases of alleged cannibalism against political foes in Europe, in AD 41, 1343, and 1672, over a span of 1,631 years, that I have read of. Are those the only such cases that happened, or were they only a small minority of a large number of cases of cannibalism that actually occurred in Europe in that era?
It is said that when former King of France Louis XVI was guillotined in 1793, some onlookers in the crowd dipped their handkerchiefs in his blood.
And this appears to be confirmed by genetic tests on the alleged blood of Louis XVI stored in a gourd.
And somewhere on the internet I read that many who soaked up Louis XVI's blood did so according to the superstition that royal blood had magical healing properties. And thus they would have had medicinal uses for the blood. If drinking someone's blood counts as medicinal cannibalism, then there could have been cases of cannibalism with the blood of louis XVI. And possibly with the blood of other beheaded persons.
And there is also this statement:
.. Conradin (1252-1268), their son, was Duke of Swabia and King of Sicily in 1266. However, his kingship was opposed by Charles of Anjou who had the support of Pope Urban IV. Conrad took up arms to keep his throne, but was defeated and captured. He was beheaded on October 28, 1268. His body was dismembered and pieces of his flesh were passed around to the watching crowd, at age sixteen (16).
And I think that this is probably just a story which appeared, perhaps centuries ago and yet still in the more recent part of the 753 years between 1268 and 2021.
And if pieces of Conradin's flesh were passed around to the crowd, what was the purpose? To handle the pieces and then pass them on? To keep them as souveieers? To eat?