That's a fair question. I'm not advocating "linguistic relativism", though; I'm saying that social categories are creating though ongoing social interactions (not limited to language). I still insist my analogy is apt: just as the psychological characteristics of someone in a hunting and gathering society cannot make that person a capitalist, the sexual desires and preferences of someone in a society without the stable sexual identity "gay" cannot make a person gay. Identities are possible because of certain patterns of social relations. In my view, this is a crucial sociological insight: people do not initially have identities, which are then disrupted/distorted/twisted by social influences; rather, social interactions make possible the creation of individual identities. (--Looking glass self.)
So if you show me a society in which people have distinct, stable sexual identities, and that norm is clearly enforced and passed from generation to generation by agents of socialization, I will say that gay people exist in that society. --And just the contrary for societies that do not identify people as belonging to distinct, stable sexual categories.
This is an empirical/historical/anthropological question, in all cases.
MIles