Of course, this has as much veracity as the idea that the Earth is flat or that the Sun and planets revolve around it, but there's a lot of people who believe it.
It seems to me that the purpose of the "born with it" argument is to develop empathy among people who lack understanding. Because it helps explain why people act on their feelings, even if they are not a good idea. We can all relate to the power of lust, love etc. It is an important point to make. But that argument only has relevance to people who find it distasteful in the first place. The argument is a reaction to homophobia.
Also, remember that a lot of people (particularly religious ones) want to regulate social behavior, even in the bedroom, because they believe this is important for society's survival and prosperity. So in their view, homosexuals should be oppressed (either strongly by the state, or more weakly by social pressure) for the good of society, and to keep their behavior from "spreading". There's not really a way to counter this mentality by people like us because their worldview is so entirely alien to us: we don't believe in divine retribution for "immoral" behavior (a la Sodom & Gomorrah) and they do, and nothing's going to shake their belief.
As you hint at up above, there are non-religious people who believe regulating sexual behavior is important for society. Do you have a way to counter that idea when it's based on a secular worldview which is not so alien to yours?
One reason might be that they believe that having a culture which is hedonistic toward sex is harmful for society, and they believe that acceptance of homosexual behavior necessarily leads to having such a culture.
>presumably Stalinists?
That is definitely not a reasonable assumption to make.
>but if you're not religious and don't believe in utilitarianism, what exactly is the goal for your society?
It is perfectly possible to be utilitarian, non-religious, and opposed to the acceptance of homosexuality. All it takes is a belief that acceptance of homosexuality is on the whole and over time more harmful for people than intolerance of homosexuality.