A number of Catholic saints have expressed authentic teaching on human sexuality and have spoken against the disordered nature of homosexuality.

St. Augustine:

All passions are dishonorable, for the soul is even more prejudiced and degraded by sin than is the body by disease; but the worst of all passions is lust between men…. The sins against nature are more difficult and less rewarding, since true pleasure is only the one according to nature. But when God abandons a man, everything is turned upside down!

Therefore, not only are their passions [of the homosexuals] satanic, but their lives are diabolic….. So I say to you that these are even worse than murderers, and that it would be better to die than to live in such dishonor. A murderer only separates the soul from the body, whereas these destroy the soul inside the body.

Those offenses which be contrary to nature are everywhere and at all times to be held in detestation and punished; such were those of the Sodomites, which should all nations commit, they should all be held guilty of the same crime by the divine law, which hath not so made men that they should in that way abuse one another. For even that fellowship which should be between God and us is violated, when that same nature of which He is author is polluted by the perversity of lust.

Saint Bernardine of Siena:

No sin has greater power over the soul than the one of cursed sodomy, which was always detested by all those who lived according to God….. Such passion for undue forms borders on madness. This vice disturbs the intellect, breaks an elevated and generous state of soul, drags great thoughts to petty ones, makes [men] pusillanimous and irascible, obstinate and hardened, servilely soft and incapable of anything. 

Furthermore, the will, being agitated by the insatiable drive for pleasure, no longer follows reason, but furor…. Someone who lived practicing the vice of sodomy will suffer more pains in Hell than any one else, because this is the worst sin that there is.

Saint Catherine of Siena:

But they act in a contrary way, for they come full of impurity to this mystery, and not only of that impurity to which, through the fragility of your weak nature, you are all naturally inclined (although reason, when free will permits, can quiet the rebellion of nature), but these wretches not only do not bridle this fragility, but do worse, committing that accursed sin against nature, and as blind and fools, with the light of their intellect darkened, they do not know the stench and misery in which they are. It is not only that this sin stinks before me, who am the Supreme and Eternal Truth, it does indeed displease me so much and I hold it in such abomination that for it alone I buried five cities by a divine judgment, my divine justice being no longer able to endure it. This sin not only displeases me as I have said, but also the devils whom these wretches have made their masters. Not that the evil displeases them because they like anything good, but because their nature was originally angelic, and their angelic nature causes them to loathe the sight of the actual commission of this enormous sin. 

Saint Thomas Aquinas:

Given the sin of impiety through which they [the Romans] sinned against the divine nature [by idolatry], the punishment that led them to sin against their own nature followed…. I say, therefore, that since they changed into lies [by idolatry] the truth about God, He brought them to ignominious passions, that is, to sins against nature; not that God led them to evil, but only that he abandoned them to evil….

If all the sins of the flesh are worthy of condemnation because by them man allows himself to be dominated by that which he has of the animal nature, much more deserving of condemnation are the sins against nature by which man degrades his own animal nature….

Man can sin against nature in two ways. First, when he sins against his specific rational nature, acting contrary to reason. In this sense, we can say that every sin is a sin against man’s nature, because it is against man’s right reason….

Secondly, man sins against nature when he goes against his generic nature, that is to say, his animal nature. Now, it is evident that, in accord with natural order, the union of the sexes among animals is ordered towards conception. From this it follows that every sexual intercourse that cannot lead to conception is opposed to man’s animal nature.

However, they are called passions of ignominy because they are not worthy of being named, according to that passage in Ephesians (5:12): ‘For the things that are done by them in secret, it is a shame even to speak of.’

For if the sins of the flesh are commonly censurable because they lead man to that which is bestial in him, much more so is the sin against nature, by which man debases himself lower than even his animal nature.

St. Peter Canisius

As the Sacred Scripture says, the Sodomites were wicked and exceedingly sinful. Saint Peter and Saint Paul condemn this nefarious and depraved sin. In fact, the Scripture denounces this enormous indecency thus: ‘The scandal of Sodomites and Gomorrhans has multiplied and their sins have become grave beyond measure.’ So the angels said to just Lot, who totally abhorred the depravity of the Sodomites: ‘Let us leave this city….’ Holy Scripture does not fail to mention the causes that led the Sodomites, and can also lead others, to this most grievous sin. In fact, in Ezechiel we read: ‘Behold this was the iniquity of Sodom: pride, fullness of bread, and abundance, and the idleness of her, and of her daughters: and they did not put forth their hand to the needy, and the poor. And they were lifted up, and committed abominations before me; and I took them away as thou hast seen’ (Ezech. 16: 49-50). Those unashamed of violating divine and natural law are slaves of this never sufficiently execrated depravity.” 12

Saint Peter Damian from the Book of Gomorrha

This vice strives to destroy the walls of one’s heavenly motherland and rebuild those of devastated Sodom. Indeed, it violates temperance, kills purity, stifles chastity and annihilates virginity … with the sword of a most infamous union. It infects, stains and pollutes everything; it leaves nothing pure, there is nothing but filth …

This vice expels one from the choir of the ecclesiastical host and obliges one to join the energumens and those who work in league with the devil; it separates the soul from God and links it with the demons. This most pestiferous queen of the Sodomites [which is homosexuality] makes those who obey her tyrannical laws repugnant to men and hateful to God … It humiliates at church, condemns at court, defiles in secret, dishonors in public, gnaws at the person’s conscience like a worm and burns his flesh like fire…

The miserable flesh burns with the fire of lust, the cold intelligence trembles under the rancor of suspicion, and the unfortunate man’s heart is possessed by hellish chaos, and his pains of conscience are as great as the tortures in punishment he will suffer … Indeed, this scourge destroys the foundations of faith, weakens the force of hope, dissipates the bonds of charity, annihilates justice, undermines fortitude, … and dulls the edge of prudence.

What else shall I say? It expels all the forces of virtue from the temple of the human heart and, pulling the door from its hinges, introduces into it all the barbarity of vice … In effect, the one whom … this atrocious beast [of homosexuality] has swallowed down its bloody throat is prevented, by the weight of his chains, from practicing all good works and is precipitated into the very abysses of its uttermost wickedness.

Thus, as soon as someone has fallen into this chasm of extreme perdition, he is exiled from the heavenly motherland, separated from the Body of Christ, confounded by the authority of the whole Church, condemned by the judgment of all the Holy Fathers, despised by men on earth, and reproved by the society of heavenly citizens. He creates for himself an earth of iron and a sky of bronze … He cannot be happy while he lives nor have hope when he dies, because in life he is obliged to suffer the ignominy of men’s derision and later, the torment of eternal condemnation

Saint John Chrysostom

But if thou scoffest at hearing of hell and believest not that fire, remember Sodom. For we have seen, surely we have seen, even in this present life, a semblance of hell. For since many would utterly disbelieve the things to come after the resurrection, hearing now of an unquenchable fire, God brings them to a right mind by things present. For such is the burning of Sodom, and that conflagration!…

Consider how great is that sin, to have forced hell to appear even before its time!… For that rain was unwonted, for the intercourse was contrary to nature, and it deluged the land, since lust had done so with their souls. Wherefore also the rain was the opposite of the customary rain. Now not only did it fail to stir up the womb of the earth to the production of fruits, but made it even useless for the reception of seed. For such was also the intercourse of the men, making a body of this sort more worthless than the very land of Sodom. And what is there more detestable than a man who hath pandered himself, or what more execrable?

All passions are dishonorable, for the soul is even more prejudiced and degraded by sin than is the body by disease; but the worst of all passions is lust between men…. The sins against nature are more difficult and less rewarding, since true pleasure is only the one according to nature. But when God abandons a man, everything is turned upside down!

Therefore, not only are their passions [of the homosexuals] satanic, but their lives are diabolic….. So I say to you that these are even worse than murderers, and that it would be better to die than to live in such dishonor. A murderer only separates the soul from the body, whereas these destroy the soul inside the body…..

There is nothing, absolutely nothing more mad or damaging than this perversity.

Saint Gregory the Great

Brimstone calls to mind the foul odors of the flesh, as Sacred Scripture itself confirms when it speaks of the rain of fire and brimstone poured by the Lord upon Sodom.  He had decided to punish in it the crimes of the flesh, and the very type of punishment emphasized the shame of that crime, since brimstone exhales stench and fire burns.

It was, therefore, just that the sodomites, burning with perverse desires that originated from the foul odor of flesh, should perish at the same time by fire and brimstone so that through this just chastisement they might realize the evil perpetrated under the impulse of a perverse desire.

St. Bonaventure

All sodomites—men and women—died all over the earth, as Saint Jerome said in his commentary on the psalm ‘The light was born for the just.’ This made it clear that He was born to reform nature and promote chastity.

Saint Basil of Caesarea:

The cleric or monk who molests youths or boys or is caught kissing or committing some turpitude, let him be whipped in public, deprived of his crown [tonsure] and, after having his head shaved, let his face be covered with spittle; and [let him be] bound in iron chains, condemned to six months in prison, reduced to eating rye bread once a day in the evening three times per week.

After these six months living in a separate cell under the custody of a wise elder with great spiritual experience, let him be subjected to prayers, vigils and manual work, always under the guard of two spiritual brothers, without being allowed to have any relationship … with young people.

St. Jerome, Doctor of the Church

And Sodom and Gomorrah might have appeased it [God’s wrath], had they been willing to repent, and through the aid of fasting gain for themselves tears of repentance.