A homosexual act is a sexual act between members of the same sex. The Catechism of the Catholic Church in paragraph 2357 teaches that Sacred Scripture "presents homosexual acts as acts of grave depravity" and that Sacred Tradition "has always declared 'homosexual acts are intrinsically disordered.'" It adds, "They are contrary to the natural law. ... Under no circumstances can they be approved." Intrinsically disordered means they're not in accord with how God designed nature to work. This means they're contrary to His Will and, therefore, always immoral regardless of why they're done.
Scripture presents sodomy as a grave depravity in both Old and New Testament. Chapter 19 of Genesis recounts the destruction of Sodom from which the term sodomy comes. Verse seven of Jude explains, "As Sodom and Gomorrah, and the neighboring cities, in like manner, having giving themselves to fornication, and going after other flesh, were made an example, suffering the punishment of eternal fire." God's directive to Moses in Leviticus 18:22 explicitly commands, "You shall not lie with mankind as with womankind because it is an abomination."
In 1 Corinthians 6:9–10, St. Paul confirms, "[N]either fornicators, nor idolaters, nor adulterers, nor the effeminate, nor liers with mankind, ... shall possess the kingdom of God." In 1 Tim 1:9–10, St. Paul writes, "[T]he Law is not made for the just man but for the unjust and disobedient, for the ungodly and for sinners ... for fornicators, for them who defile themselves with mankind."
In chapter one of Romans, St. Paul teaches that God may permit homosexual desires to overcome men as a punishment for having rejected Him under the natural law. In Romans 1:26–27, St. Paul warns:
For this cause God delivered them up to shameful affections. For their women have changed the natural use into that use which is against nature. And, in like manner, the men also, leaving the natural use of the women, have burned in their lusts one towards another, men with men working that which is filthy, and receiving in themselves the recompense which was due to their error.
See how sodomy is rapidly becoming normalized in Church Militant's Premium show Mic'd Up—Smuggling In Sodomy.