The problem with the “gay gene would die out” theory is it assumes that no “gay” would have any children, ever.
That assumes that due to a “gay” inclination, a “gay” person would not go ahead and marry/and/or/at-least/have children, in spite of that “gay” inclination - for social reasons (peer & family pressure) and any other reason.
Yet that assumption is contrary to what has been reported by sociologists & the “gay” community for quite a long time - that in fact a sizable number of “gays” in the past DID (and some still do) marry and bare children out of the social pressures to do so.
That also is no proof that there IS a “gay” gene, but it proves that even if there was a “gay” gene, it would not have died out (at least not entirely) as “gays” would still make up some portion of the child bearing population, in spite of their “gay” preference.
And even more telling, genetically, is IF there was (A BIG IF as there is no proof pf a “gay” gene) a “gay” gene that was only “activated” when some other gene was also present, making a condition where the “gay” gene could be carried, & not always expressed but passed on.
I do not think there is any proof of a “gay” gene. But the theory that it would “die out” is in error and is not a proof that there is not one.
You did not read the article in its entirety, did you? The author discusses this point.