I'm not going to disagree with this, but I'd argue that condemnatory Christian responses towards gay people haven't historically reflected this perspective. If you look at what they actually have said, it's that gay people are the products of molestation, sexual abuse, or dysfunctional family dynamics. Or they use falsified research and unscientific magazine surveys to make general claims about the prevalence of unrealistic sexual practices involving rodents in places they wouldn't go, to make up lies about the effects of actual sexual practices, the prevalence and causes of mental illness among gay people, reductions in average lifespan by gay men, the negative results of children being raised in gay homes, and so forth. Or they fight tooth and nail against anti-bullying measures specifically because the idea of gay children being accepted is anathema to them. It says something that the same people from the same organizations that have been telling the same lies for decades are responsible for the situation in Uganda, and that campaign was just as based in animus as any of the campaigns here have ever been.
They don't actually spend a lot of time talking about the inherent evil of a man being with another man or a woman being with another woman so much as they spend time trying to convince people by dint of lies that gay people are actually engaged in disgusting, degenerate, and immoral-on-their-own-terms behaviors. And you just don't see that sort of vitriol directed towards alcoholics, even inveterate alcoholics who haven't admitted they have a problem.
I'll admit that there's a difference between the misled (the rank and file, by and large) and the people who have promulgated that nonsense, but to the extent that these attitudes have been broadly supported by conservative Christian institutions and organizations supported by that rank and file, I don't feel especially charitable here.
FWIW, I'm pretty sure most historical belief that there must be "something wrong" with homosexuality to put it on a par with things like excessive promiscuity (which can spread STDs, cause problems with paternity, foment jealousy and discontent, etc.), gambling, drug use, and alcoholism is the simple fact that the idea of engaging in homosexual behavior revulses most straight people, for reasons likely largely evolutionary, so to see two men or two women kissing or fucking is to see two individuals crossing what is a pretty sharp line shared by a solid majority of people.
So in the case of Christians stigmatizing homosexuals via pseudoscience, pseudopsychology, pseudosociology, and other pseudo disciplines, well, there has never been a major social movement to normalize and even celebrate alcoholism. Not to mention that it's possible to enjoy alcohol and fatty foods on occasion without abusing them, meaning the average person has a personal bridge to problems like alcoholism and gluttony, can relate to those problems in some way. Yet in the case of homosexuality, we have seen not only a normalization of open homosexuality in the past 40 years, but a downright fascination with it - from gay characters, to entire gay genres of art and entertainment. Christians' faith is in a book that explicitly condemns homosexual behavior, a commandment that is undergirded by that common "Ew" reaction, so they have a pretty solid reason, from their perspective, to expect that the structure of reality more generally will align with that two-ply feeling.
So yes, you're right that, historically, Christians' arguments contra homosexuality have been about more than mere abstract moral objection, that they have attempted to co-opt the language of science in order to hold back progress toward great equality, but at its root, this phenomenon isn't much more than garden-variety confirmation bias, which is a problem that afflicts pretty much every human on the planet, meaning I think at least some slack can be cut to them for engaging in it, even given the rather shitty byproduct of it in this case.