You've studied the philosophical underpinnings of the Church's view of sexual morality? Or, for that matter, the philosophical arguments of literally the last 4000 years of human history until the 20th century concerning this issue? Aristotle? Aquinas? Or are you, as most people do, just subscribing to some sort of vague, unjustified consequentialism and so are assuming that every other argument that doesn't fall into this consequentialism must not exist or just be patently incorrect?
Again with the arrogance. You don't know my life history (nor would there even be any way to verify it since we're ships passing in the night). Since you asked, though, yes, I have. I grew up in one of the primary religious areas in the United States, with nearly every waking moment in the Church during my youth; in a place where Christ took precedence even over the school system and everything was viewed through the lens of scripture. My undergraduate days included theology classes as the topic interested me so much I thought it a welcome break from economics. My best friend from childhood is married to a person who literally is responsible for restoring and preserving some of the earliest copies of the Bible for certain shall-not-be-named European institutions. These sorts of debates and discussions, particularly as it pertains to sexuality given it was the zeitgeist at the time, have been a very big part of my life and friendships, down to even my work in economics (the morality of usury, in particular, and how that relates to a banking system built upon debt). But your desire for confirmation bias is so strong you can't even imagine that, can you? You assume that nobody can be as experienced, or as well read, as you. It's severely unattractive. Don't be that certain about things which you cannot know.
I mean, for heaven's sake, bringing up Aquinas? The man was a sex addict working through his own compulsive behavior issues and attempting to come up with some moral framework that allowed him to get a handle on compulsions that had completely consumed his life in what is now a pattern so normal, and such an ordinary part of broke brains, researchers know about it (look at former drug addicts or alcoholics, who have personalities that tend to extremism and cause them to go in the opposite direction once reformed - it's the only way they can contain themselves). To think he had any reasonable points on the morality of sexuality is demonstrative of a non-rational mind. They were the intellectual masturbation of a broken man searching for control mechanisms and meaning to keep himself from his own destruction, nothing more.
This simply isn't true. There are tomes dedicated to discussing sexual morality, including the immorality of homosexual behavior. And from this ignorance, you then make the positive claim that it's all really just based in "prejudice." The Church, in particular, has provided purely philosophical arguments addressing just this issue.
And I can guarantee that I have read more than you on the topic. None of it is convincing. It is all a conclusion in search of evidence. It is ancient bigotry, based on utterly false beliefs about the nature of human sexuality, masquerading as high minded prose. Unlike nearly every other moral command, it cannot stand on its own, based entirely upon evidence, outside of faith. We, as a civilization, have discarded all others - mixed linens, bans on shellfish, etc., - and this is the last that remains. We're in that period of transition, now, where most who had a problem with it in the United States are dying off.
I'm trying to have compassion for you because there is little reason to think you will avoid the behavior pattern that people in your particular brand of mental chains follows. Unless you are fortunate enough to be asexual, you will attempt celibacy, reject healthy emotional connections, break in weakness, and engage in bouts of short-term hedonism that may very well destroy your life and require you to feel the need for repentance.
While other men who happen to be gay are out there getting engaged, celebrating weddings, having their kid's first birthday party, going to school plays, taking vacations, and debating which color paint they should use on the new front door, you will be alone.
They'll be falling asleep next to the love of their lives, cooking dinner, celebrating promotions at work, and building a life that matters, while you will be alone.
When they are old, with wrinkled hands, sitting together on the front porch watching their grandkids play in the yard, knowing they've had a lifetime together, you will be alone.
Despite the harm your attitude causes real people, you are just as much a victim of this brainwashing. It is heartbreaking. I mean that literally, not as some sort of general Internet phrase. My heart literally aches for you. It's madness what you've deluded yourself into believing based entirely on social proof of those around you.
On some level, you have to know this. Otherwise you wouldn't lie to yourself by saying things like:
In fact, the vast majority of people I know who are in relationships are hardly happy all (or even most) of the time.
That's not normal. You're telling yourself what you need to hear to keep up the walls of confirmation bias. Good luck. I doubt it will end well. It never does.