The motivation is mostly religious.
Homosexuality must be a choice, otherwise God created homosexuals as they are, and homosexuality is just another part of Nature.
But if that's true, homosexuality can't be a sin, because sin is always a choice.
But homosexuality is a sin because the Bible says it is (even though it doesn't really,) therefore it must be a choice.
P: Sex outside of marriage is a sin.
Q: Marriage is between a man and a woman.
Therefore [P and Q] implies that homosexual activity is wrong but the mere act of being attracted to the same sex is not inherently sinful.
As for why that should influence our votes for public policy, the reasoning goes that sin always brings trouble, death, and non-well-being to society, therefore influencing public policy away from sinful societal patterns and acts is one important way to love one’s neighbors, since it will result in greater well-being for them.
Also, why do you feel the Christian sacred texts doesn't really condemn homosexuality? I feel you have to do a lot of extra-textual analysis and theory-crafting to reach that perspective, so it's no surprise that Christians in general don't buy that idea.
And... it also condemns masturbation, marrying foreigners, eating fish, letting menstruating women inside the city limits and mixing fabrics.
Someone living in Biblical times probably wouldn't have any concept of someone being "straight" or "gay," just of someone following cultural norms or violating cultural taboos. So to say the Bible condemns homosexuality is a misappropriation of the intent of the text outside of the cultural and temporal context to which it was intended to apply.
This comment you're reading has a dead sibling that pointed out the commonly-held Christian doctrine that some of the Bible's laws don't apply to modern Christians.
The commenter is absolutely correct, and here is a link from a famous and well-regarded theologian on the subject (R.C Sproul).
https://www.ligonier.org/learn/articles/which-laws-apply/
In summary, there are civil, ceremonial, and moral laws in the Old Testament. For example, "no murder" is a moral law, while dietary restrictions are a ceremonial law.
I'm not commenting on the validity or "correctness" of this doctrine, as I am not a theologian. I just think it's worth confirming that this is something a lot of Christians believe.
In general, NT has plenty of stuff that can be appropriated for fire-and-brimstone preaching. Most of it is Paul's, which is why some consider Pauline Christianity to be a mutilation of what was preached before.
[0] never met Christ, so he had to pretend he had some sort of vision to get in the club... Jesus treated the money changers better than He would have treated Paul.
There is a very convenient Christian doctrine where there are "three types of law in the Bible", which explains that some rules are meant for Israelites and some are meant for everyone (and you [or the church] basically get to guess which apply to you).
It always read to me that it was more about turning men into women than it was about actually performing homosexual acts.
When you say "homosexuality" do you mean homosexual proclivities, or homosexual acts? It's an important nuance.
Judiasm/Christianity/Islam teaches that humans have a proclivity to sin (fallen nature), but God commands them to not sin, i.e. to act ccontrary to their nature.
There is no theological contradiction (or least, not anymore than normal) between natural homosexuals and God forbidding homosexual acts.
EDIT: The actual consequence of natural homosexuality is a difference of understanding. Birth condition vs self-inflicted. "Crack baby" vs "crack head".
Not if you believe in total depravity combined with unconditional election. Which just happens to be the cornerstone dogmas of one very popular Christian denomination.
I understand what you mean, but it doesn't seem to be the case. In regards to sexual preferences, for example, there are some that are, arguably, not a choice either, and still are considered absolutely forbidden.
> For example you and I are against Down's syndrome, but we can't make any progress by telling people to stop having it.
Nope, that would be ridiculous. But at the same time having Down's syndrome is not devoid of legal consequences. You'll probably be denied a driving license or the possibility to own guns, and you can argue as much as you want that your condition is perfectly natural and you didn't have a choice, it won't make any difference.
There doesn't seem to be much evidence that sexuality can be changed by conscious choice. So if your sexuality runs along those lines you're going to have a bad time, because you'll either have to repress your urges, or risk actions that damage others, possibly with criminal consequences.
The edge cases of this can become ridiculous - but still tragic. E.g. there are people who are primarily turned on by paving stones and/or drain covers.
It's not really obvious what "natural" means in this context. Is this imprinting? Genetics? Something else? There aren't any good answers. Criminal law does the best it can with them, but it's not clear that choice really applies, and criminal punishment is pointless and ineffective anyway - either as a deterrent or as rehabilitation.
The bigger moral question is maybe why some social groups seem obsessed with what they consider sexual deviance - including their beliefs about homosexuality - while apparently ignoring other moral and social questions.
What is the psychological process that turns homosexuality into a uniquely disturbing moral problem for them, while other hot-button issues - poverty, diet, government and corporate corruption, take your pick from a long list - are relatively uninteresting for them?