Why isn't the Spanish bullfight immoral, according to Catholicism?

Consider what The Catholic Encyclopedia says about Animal Cruelty:

The Scholastics

The scholastic theologians condemn the infliction of needless suffering on animals, chiefly because of the injurious effects on the character of the perpetrator. Thus St. Thomas, in his Summa Contra Gentiles (Book II, 112), after refuting the error that it is not lawful to take the lives of brutes, explains the import of the above-mentioned texts of Scripture. He says that these prohibitions are issued either "lest anyone by exercising cruelty towards brutes may become cruel also towards men; or, because an injury to brutes may result in loss to the owner, or on account of some symbolic signification."
…

Catholic doctrine

…
Only a person, that is, a being possessed of reason and self-control, can be the subject of rights and duties; or, to express the same idea in terms more familiar to adherents of other schools of thought, only beings who are ends in themselves, and may not be treated as mere means to the perfection of other beings, can possess rights.
…
We are bound to act towards them in a manner conformable to their nature. We may lawfully use them for our reasonable wants and welfare, even though such employment of them necessarily inflicts pain upon them. But the wanton infliction of pain is not the satisfaction of any reasonable need, and, being an outrage against the Divinely established order, is therefore sinful.
…
While Catholic ethical doctrine insists upon the merciful treatment of animals, it does not place kindness towards them on the same plane of duty as benevolence towards our fellow-men. Nor does it approve of unduly magnifying, to the neglect of higher duties, our obligations concerning animals. Excessive fondness for them is no sure index of moral worth; it may be carried to un-Christian excess; and it can coexist with grave laxity in far more important matters. There are many imitators of Schopenhauer, who loved his dog and hated his kind.
…
— CATHOLIC ENCYCLOPEDIA: Cruelty To Animals

It does condemn "the wanton infliction of pain", which is not for the satisfaction of any reasonable need.

But:

• It refrains from saying what is "reasonable need", or how much violence or unnecessity is required to be "wanton".
• It allows inflicting pain for "reasonable wants" (and who's to say that bullfighting isn't a reasonable want?).
• Cruelty and needless suffering are condemned only because of the possible effect on the perpetrator.
• Cruelty might result in financial loss (e.g. if a useful animal dies).
• Animals do not have rights.

Clearly there is no doctrinal or other offical stance against cruelty to animals, except in as far as it directly or indirectly affects humans.

With bullfighting in particular (as shown in Ken Graham's answer), the only concerns about pain, injury, or death are with respect to their being experienced by humans.
And who could argue that with bulls, aggression and violence are not "conformable to their nature"?

Why is it not outright forbidden for faithful to attend Spanish bullfights?

The short answer is that it is complicated!

I believe that most Catholics would consider Spanish bullfighting immoral. At least, at first glance.

But before truly diving into the subject matter, it has to be understood that different types of bullfighting exist, even in Spain. Some are not blood letting at all.

Bullfighting is a physical contest that involves a bullfighter and animals attempting to subdue, immobilize, or kill a bull, usually according to a set of rules, guidelines, or cultural expectations.

There are several variations, including some forms which involve dancing around or leaping over a cow or bull or attempting to grasp an object tied to the animal's horns. The most well-known form of bullfighting is Spanish-style bullfighting, practiced in Spain, Portugal, Southern France, Mexico, Colombia, Ecuador, Venezuela, and Peru. The Spanish Fighting Bull is bred for its aggression and physique, and is raised free-range with little human contact.

Styles

Originally, at least five distinct regional styles of bullfighting were practised in southwestern Europe: Andalusia, Aragon–Navarre, Alentejo, Camargue, Aquitaine. Over time, these have evolved more or less into standardized national forms mentioned below. The "classic" style of bullfighting, in which the rule is kill the bull is the style practiced in Spain and many Latin American countries.

Bullfighting stadia are named "bullrings". There are many historic bullrings; the oldest are the 1700s Spanish plazas of Sevilla and Ronda. The largest bullring is the Plaza México in Mexican capital which seats 48,000 people.

Spanish

Spanish-style bullfighting is called corrida de toros (literally "coursing of bulls") or la fiesta ("the festival"). In the traditional corrida, three matadores each fight two bulls, each of which is between four and six years old and weighs no less than 460 kg (1,014 lb).[13] Each matador has six assistants: two picadores (lancers on horseback) mounted on horseback, three banderilleros – who along with the matadors are collectively known as toreros (bullfighters) – and a mozo de espadas (sword page). Collectively they comprise a cuadrilla (entourage). In Spanish the more general torero or diestro (literally 'right-hander') is used for the lead fighter, and only when needed to distinguish a man is the full title matador de toros used; in English, "matador" is generally used for the bullfighter.

Recortes

Recortes, a style of bullfighting practiced in Navarre, La Rioja, north of Castile and Valencia, has been much less popular than the traditional corridas. But recortes have undergone a revival in Spain and are sometimes broadcast on TV.

This style was common in the early 19th century. Etchings by painter Francisco de Goya depict these events.

Recortes differ from a corrida in the following ways:

• The bull is not physically injured. Drawing blood is rare, and the bull is allowed to return to his pen at the end of the performance.

• The men are dressed in common street clothes rather than traditional bullfighting dress. Acrobatics are performed without the use of capes or other props. Performers attempt to evade the bull solely through the swiftness of their movements.

• Rituals are less strict, so the men have the freedom to perform stunts as they please. Men work in teams but with less role distinction than in a corrida.

• Teams compete for points awarded by a jury. Since horses are not used, and performers are not professionals, recortes are less costly to productions.

Comic bullfighting

Comical spectacles based on bullfighting, called espectáculos cómico-taurinos or charlotadas, are still popular in Spain and Mexico. Troupes include El empastre or El bombero torero.

Encierro

An encierro or running of the bulls is an activity related to a bullfighting fiesta. Before the events that are held in the ring, people (usually young men) run in front of a small group of bulls that have been let loose, on a course of a sectioned-off subset of a town's streets.

Toro embolado

A toro embolado (in Spanish), bou embolat (in Catalan), roughly meaning "bull with balls", is a festive activity held at night and typical of many towns in Spain (mainly in the Valencian Community and Southern Catalonia). Balls of flammable material are attached to a bull's horns. The balls are lit and the bull is set free in the streets at night; participants dodge the bull when it comes close. It can be considered a variant of an encierro (correbous in Catalan). This activity is held in a number of Spanish towns during their local festivals.

One of the biggest defaults for not having bullfighting declared immoral is due to a more clearer understanding of all elements to be completely understood, including those of a historical, a cultural and a moral perspective perspectives to be taken into consideration.

The authorities of the Catholic Church have often condemned bull-fighting. Even St. Pius V prohibited this form of amus*m*nt everywhere, threatening with many penalties the princes who countenanced it, as well as the performers and spectators, especially clergymen and religious. But in Spain today these prohibitions are no longer in force since the constitution of St. Pius V for Spanish laymen, and Clement VIII (Bull "Suscepti muneris", 12 January, 1597) reduced it to a jus commune, limiting the prohibition to holidays and to the clergy.

Although Pope st. Pius V condemned bullfighting as “a spectacle for demons rather than men” in his Apostolic Constitution De salute of November 1st, 1567.

The [Catholic Encyclopedia has the following to say on the morality of bullfighting:

The morality of the bullfight

Bull-fights have occasioned many accusations of barbarity against the Spaniards.

• The reason for this is, first, an utter ignorance of a game in which man with his reason and dexterity overcomes the brutal strength and ferocity of the bull. Foreigners as a rule think that the Spanish populace go to the bull-fight to witness the shedding of human blood. This is false. Generally there are no casualties; and when an accident does occur, no one derives pleasure from it; on the contrary, all deplore it.

• Second, the misconception implies a lack of comparison with other spectacles. The risks taken by acrobats, tight-rope dancers, and tamers of wild beasts are no less barbarous than those of the bull-fight, although the performances themselves are less diverting. And prize-fighting is surely much more brutal, seeing that the vanquished is a human being and not a brute.

• Lastly, the modern theatre is frequently more evil in its effects than bull-fighting, which, whatever else may be said of it, arouses no immoral or anti-social passions.

The authorities of the Catholic Church have often condemned bull-fighting. St. Pius V (1 November, 1567, Const. "De salute") prohibited this form of amus*m*nt everywhere, threatening with many penalties the princes who countenanced it, as well as the performers and spectators, especially clergymen and religious. But in Spain today these prohibitions are not in force. Gregory XIII (23 August, 1575, "Exponi") moderated the constitution of St. Pius V for Spanish laymen, and Clement VIII (Bull "Suscepti muneris", 12 January, 1597) reduced it to a jus commune, limiting the prohibition to holidays and to the clergy.

Now seeing that Pope Gregory allowed limited viewing of bullfighting is not a surprise! His youth was not stainless. While still at Bologna, a son, named Giacomo, was born to him of an unmarried woman. Even after entering the clerical state he was worldly-minded and fond of display. Some historians have severely criticized Gregory XIII for ordering that the horrible massacre of the Huguenots on St. Bartholomew's Day in 1572 be celebrated in Rome by a "Te Deum" and other marks of rejoicing.

This it is time for another pope to step up to the plate and declare Spanish bullfighting immoral.

But let us continue with the Catholic Encyclopedia:

Moralists as a rule are of the opinion that bull-fighting as practised in Spain is not forbidden by the natural law, since the skill and dexterity of the athletes precludes immediate danger of death or of serious injury (cf. P.V, Casus conscientiae, Vromant, Brussels, 1895, 3d ed., I, 353, 354; Gury-Ferreres, Comp. Th. mor., Barcelona, 1906, I, n. 45). Even in Spain and Spanish America they have been forbidden to clergymen and religious, by Pius V, as well as by the Plenary Council for Spanish America (n. 650; cf. also C. prov., Vallisol., I, p. 5, tit. 1, n. 11). The Bishop of Ciudad Rodrigo received the same answer from the Penitentiaria (19 September, 1893).

It is false to say that the Spanish clergy encourage these spectacles. Although public festivals are celebrated with religious ceremonies as well as bull-fights, the clergy is in no-wise responsible for this. If both are announced on the same bill poster, the authorities, or particular associations, are responsible for the printing of this, not the clergy.

It is worthy of note that foreigners who have been present at bull-fights are not so harsh in their judgments as those who have formed an opinion from what they have heard about them from the societies for the prevention of cruelty to animals.

The question that remain I say that Rome has to see bullfighting as a genuine form of cruelty to animals!

**Cardinal Manning’s writings on animal cruelty are an eye opener. May future popes see the light.

With more feeling, but with no less exactness, the late Cardinal Manning expressed the same doctrine:

It is perfectly true that obligations and duties are between moral persons, and therefore the lower animals are not susceptible of the moral obligations which we owe to one another; but we owe a seven-fold obligation to the Creator of those animals. Our obligation and moral duty is to Him who made them and if we wish to know the limit and the broad outline of our obligation, I say at once it is His nature and His perfections, and among these perfections one is, most profoundly, that of Eternal Mercy. And therefore, although a poor mule or a poor horse is not, indeed, a moral person, yet the Lord and Maker of the mule is the highest Lawgiver, and His nature is a law unto Himself. And in giving a dominion over His creatures to man, He gave it subject to the condition that it should be used in conformity to His perfections which is His own law, and therefore our law (The Zoophilist, London, 1 April, 1887).

While Catholic ethical doctrine insists upon the merciful treatment of animals, it does not place kindness towards them on the same plane of duty as benevolence towards our fellow-men. Nor does it approve of unduly magnifying, to the neglect of higher duties, our obligations concerning animals. Excessive fondness for them is no sure index of moral worth; it may be carried to un-Christian excess; and it can coexist with grave laxity in far more important matters. There are many imitators of Schopenhauer, who loved his dog and hated his kind.

We all have to change our perspectives at times, this includes the Church!