The assumption that there is a biological predisposition to homosexuality is not proven, and most evidence suggests that there are significant environmental factors that can also come into play ( a history of molestation or abuse, familial role models, etc.,). Even if we accept that genetic predispositions are present, then the individual may be more likely to engage in a given conduct (again, not proven, but possible), but that doesn't mean that the conduct is a positive thing. There are genetic indicators for chemical addictions, for example, but we don't have the state give out cocaine or heroin to those who give in to those predispositions, and we certainly prosecute those who enable them through sales of drugs. Just because a behavior may be the result of a genetic predisposition does not mean that society has to embrace or encourage that behavior.
Given the higher mortality levels associated with homosexuality, the higher rates of domestic violence and the promiscuity endemic in gay culture, even among those in supposedly committed relationships, and the consequent greater incidence of communicable diseases, there is no compelling interest for the state to encourage these behaviors. This is not an argument for persecution of gays, who are human beings and citizens, entitled to the same legal protections from the state as the rest of us, but to go from that to arguing that their behavior is biologically based, and therefore must be accepted and embraced by everyone, and that anyone who sees any differences is a bigot, is irrational.