Homosexuals are the progeny of heterosexuals. For instance, if my daughter turns out to be a lesbian, she will be as capable as any other woman to contribute to any society, large or small.
Furthermore, homosexuals do marry and have children, especially when that’s necessary for the survival of their society. In poor societies where children are considered to be their “social security” and “medicare” wrapped into one, most homosexuals marry and procreate
She'll also have a limited lifespan as opposed to a heterosexual woman, a greater likelihood for drug abuse, suicide, and emotional disorders.
Homosexuals cannot survive without heterosexuals. Your statement that many homosexuals do marry and have children. That's not the point. It's their behavior as homosexuals that is dangerous and destructive to society.