Removal of Homosexuality Through Natural Selection

Since Ward put up his question of whether the homosexual lobby would allow parent to genetically manipulate their children into heterosexuals, I've been thinking homosexuality from an evolutionary point of view. Now, I am a Christian and I don't accept most of the claims of evolutionary theory, but it's interesting that it is the secularists - who believe in evolution - that are most pushing for gay rights. Here's what I mean, the theory of natural selection as I understand it says that only species and genetic structures that prove to be productive will survive. Anything that is not useful or leading toward the next evolutionary change is selected out and left behind. From this idea it seems to me that homosexuality - if it is genetic - would eventually be selected out because it does not aid in the reproduction and growth of the human species. Maybe I'm not understanding the concept of natural selection, but it seems that people that are in favor of the theory of natural selection should not be the people pushing for an understanding of homosexuality as genetic - simply because homosexuals will eventually become a victim of evolutionary natural selection. The NY Times has an opinion piece on this (from a distinctly NY Times POV), from the sound of it, evolutionists are looking for a way around natural selection when thinking about homosexuals. Maybe genetic manipulation is the next level of natural selection - except this time it would be a more conscious evolution than before. Thoughts?