There is no percentage so small that it justifies alienation by the majority. In fact, the Kinsey report demonstrated a spectrum of sexual orientations. AIDS has been a big killer. Epidemiology studies from public health offices across the country show that AIDS does not care about the sexual orientation of the person it attacks. Gay people without AIDS live as long as anybody else in the general population.
Monogamus marriage is just as healthy for gay and lesbian couples as it is for heterosexual couples.
Unfortunately laws do not permit gays and lesbians to marry, so fewer of them can find and maintain a monogamus relationship than can heterosexuals. The public health issue here is caused by a legal discrimination, not a sexual orientation. Tragically, it is true that many homosexuals die at a young age from murder and suicide. I submit that these young deaths are direct indictments against the groups that perpetuate hate. There is no conclusive evidence yet that either heterosexuality or homosexuality are caused by a biological factor.