(Parts of this page need revision after Welcome to Estonia)
When we assume that the main purpose of a human is to reproduce, then the optimal sexual orientation for a man is to perceive women as attractive and for a woman to perceive men as attractive. This optimal orientation avoids individuals wasting energy in sexual efforts towards a partner of same sex, which would be useless.
If you continue this thought with a politically right-wing mind, you come to the conclusion that a healthy civilization should repress homosexuality because it is at best a suboptimal development that at worst a sin against divine laws, which subvert and potentially harm human civilization.
But things get more complex when you consider that the meaning of life is more than having children, and that increasing our population (the number of individual humans living on earth) is not a primary concern of our species.
The Catholic Church has no problem with marrying a couple who know that they won’t have any biological children together, e.g. for medical reasons. Such a couple may have other kinds of “children”: they can adopt orphaned children, they can work together on spiritual “children” (a project or a vision) or invest into material “children” (a house or a car).
This shows that a marriage makes sense also without sex and without biological children.
So I see no problem to allow for same-sex marriage as well. I can imagine that the Church will one day recognize same-sex marriage as a variant that deserves the same benediction as any other marriage. But we are not yet there.
There are homosexual people who agree to form a couple and even to adopt and raise children in a family-like environment. There is nothing wrong with this. It is great and deserves our support and benediction. Because children having a homosexual couple as parents are still far better off than children who grow up with only one parent. Homosexual people should have a right to form a civil union, to marry and to adopt and raise children.
There is a theory that homosexuality might be “nature’s population control so that we don’t overpopulate.” Richard Dawkins responded to this idea on Darwin Day 2015. He explains that evolution “doesn’t work like this” because it works on the level of the genes of an individual. He concludes with a –for a Britain– surprisingly clear verdict: “So I am afraid that it couldn’t be true that homosexuality is an adaptation to keep the population size down.”“
See also About family.
“When it comes to homosexuality, many Christians are being stupid and unfair to both Pope Francis and Saint Paul.” – Homosexuality, Francis & the Bible, Patheos, October 2020.
“Homophobia forces many Christians to disproportionately apply ethical gravity to two obscure Greek terms while neglecting other biblical vices.” – Ethical Consistency & Homosexuality, Patheos, November 2020.
Keith Giles and Steve Scott explain that Romans 1 and 2 need to be read together: Rm 1 develops an empathic description of those hated by the readers, he “stokes the fire of condemnation” in the reader’s emotions. And then, in the second chapter, he drops the spiritual bomb on them: “If you condemn your fellow humans like this, how can you hope that God would forgive your sins?”. And something similar can happen for Romans 12 and 13: these two chapters explain that when somebody does evil against you, and when you live in a civilized state, you won’t punish them yourself but rather count on police and judge to do their work. But if you start reading at chapter 13, you can get the impression that Paul tells us to create an authoritarian government and demands that we obey all laws. The actual message is that if we commit evil, we should submit to the punishment given to us.
I commented: A great explanation! I re-read chapters 1 & 2 under this light in three different languages (German, French and Estonian) and feel that you are right. OTOH even the greatest explanation doesn’t help those who are on the other side: I forwarded the thought to a traditionalist who was angry about a bishop who add dared to co-assist the ordination of a gay pastor in a LGBT-friendly church. Her answer was “Reading the 2nd chapter doesn’t revoke the truths of chapter 1. What a pity that such academic complacency has blinded the eyes of many to the truth of God.”