At the end of the homily, Father quotes St. Alphonsus Ligouri on impurity. I don't think the exact quote is posted below but you'll understand.
HATRED, BLASPHEMY, THEFT, and IMPURITY.
..."Behold, the four gates by which the greater number of souls enter Hell; and it is of these four that I mean to speak today, in order that you may
amend and cure yourselves of these four vices, otherwise God will cure you of them, but by your own destruction.
Hell's Widest Gate: Impurity
We have now to speak of the fourth gate of Hell, which is impurity [sexual sins], and it is by this gate that the greater number of the damned enter.
Some will say that it is a trifling sin. Is it a trifling sin? It is a mortal sin. St. Antoninus writes that such is the nauseousness of this sin that
the devils themselves cannot endure it.
Moreover, the Doctors of the Church say that certain demons, who have been superior to the rest, remembering their ancient dignity, disdain tempting
to so loathsome a sin. Consider then how disgusting he must be to God, who, like a dog, is ever returning to his vomit, or wallowing like a pig in the
stinking mire of this accursed vice (2 Pet 2.22).
The impure say, moreover, "God has compassion on us who are subject to this vice, because He knows that we are flesh." What do you say? God has
compassion on this vice? But you must know that the most horrible chastisements with which God has ever visited the earth have been drawn down by this
vice. St. Jerome says that this is the only sin of which we read that it caused God to repent of having made man, for all flesh had become corrupted
(Gen 6.6-12). And so it is, St. Jerome says, that there is no sin which God punishes so rigorously, even upon earth, as this. He once sent fire from
Heaven upon five cities, and consumed all their inhabitants for this sin (Sodom and Gomorrah,Gen 18-19)."...