Historically the majority of social narratives about gay people have been social constructionist narratives.
This is different than saying the narratives have been socially constructed. Not a majority but all narratives are socially constructed. But a social constructionist narrative about gay people says that gay people are not really gay. They are a group of people who have constructed a social identity that makes them gay. There is, lurking behind every social constructionist narrative of sexual identity, an essentialist premise about the nature of human sexuality. Strict social constructionists may deny that there is an essentialist premise behind their theories. But even if that were possible, the problem is that into the intellectual vacuum created by the denial that we can actually know what anything is in itself essentialist assumptions rush. Human nature abhors a vacuum.
There are two basic essentialist premises that have typically undergirded social constructionist narratives. One is that all human beings are by nature heterosexual. In this narrative, homosexuality is caused by a fault or a flaw: usually either perverse intention on the part of the homosexual him or herself ("this man/woman sinned") or because of failed upbringing on the part of the parents ("his/her parents sinned").
The other essentialist premise behind social constructionist theories of gayness is that all human beings are, by nature, bisexual. "Normal" upbringing will inculcate the heterosexuality required for the propagation of the race; while failed upbringing will cause people to fixate on homosexual yearnings. That was basically Sigmund Freud's theory about homosexuality.
In late 19th- and early 20th-century Germany we saw a third type of essentialist premise behind a social constructionist theory of homosexuality that was embraced by the masculinist wings of the German homosexual rights movement: that all men (they were really unconcerned with women) are by nature homoerotic, and that homoeroticism is therefore the basis of all higher civilization. There's a tragic irony in that particular story, as recounted by Robert Beachy in Gay Berlin: Birthplace of a Modern Identity. Masculinist homosexuals embraced the rise of Nazism, and many hailed Hitler as the charismatic, "homoerotic" leader their theories predicted would rise in any "Männerbund" or "male society." Hitler and the Nazis, of course, did not return the favor. Adolf Brand, a leader of one of the masculinist factions of the German gay rights movement of this era saw what was happening only too late: "The former [Community of the Special] members have now given their trust and support to the very person [who] has publicly declared that if the [Nazi] Party comes to power, all homosexuals will be strung up from the gallows" (p. 239).
Social constructionist narratives are by their nature universalizing and colonizing. They tell gay people that we don't actually know what we are. Philosophical types who want to deny that anybody can know anything I'm sure find this very intellectually pleasing. But in its final analysis, when imposed on others it is patronizing and disempowering -- even annihilating. As Friedrich Radzuweit, a German gay rights activist in the 1920s and 30s protested, "the claim that human beings shared a fundamental bisexuality... undermined not only the experience and identity of most homosexuals but also the moral and pragmatic arguments for legal reform" (p. 235). The Nazis, as Beachy points out, were only too happy to embrace a social constructionist narrative of homosexuality, to justify the murder of gay men and women in Nazi concentration camps (pp. 237-238).
Is there legitimate debate and discussion about the construction of gay identities? Absolutely! Again, citing Beachy's study of the late 19th- and early 20th-century gay rights movement in Germany, we see a number of competing views. One viewed homosexuality as a "third sex," i..e., homosexuality as a gender identity (of which gay rights activist Magnus Hirschfeld was an advocate). Another insisted that to be gay is merely a sexual orientation that has nothing to do with gender identity (of which Friedrich Radzuweit was a vocal advocate, and which Hirschfeld was willing to allow). I confess I don't have much patience for the homo-supremacist, misogynist and anti-Semitic theories of people like Adolf Brand or Hans Blüher. But I'm interested in (and love to discuss) the ways we create identities on the foundation of our sexuality as we experience it.
But gay experience deserves to be treated with respect. You can tell me that my experience of my sexuality as a gay man as something that is innate, immutable, and natural is merely a social construct. Please don't be offended if I protest that you are colonizing me, that your construction of my sexuality doesn't leave me a legitimate social space.