I think NJ has it quite figured out. There is a fear among the gay community that the gene could be discovered and eradicated or fetuses aborted once it's detectable.
The great irony is, of course, that the most vehement anti-gay people are also usually the most vehement anti-abortion people. If they get prenatal testing, what would they do? What could they do? Try to force the child to be straight? Opt for some sort of gene replacement therapy?
There is a very real possibility that genetic augmentation will erase some traits from the genome simply because people want to. While we might welcome the ability to eliminate the gene for breast cancer or cystic fibrosis, might others consider eliminating genes for homosexuality? Short stature? Dark skin? If I were a parent and could give advantages to my unborn child, would I do it? Yes I want my son to never go bald, be 6' 2", prone to muscle mass, great teeth, well-hung, strikingly handsome, and have a genius IQ. These are things that could be as valuable to him as a college education given how biased society is to people we consider good-looking. Given how competitive some parents are, I don't see this as being far-fetched. At some point, perhaps not too far in the future, we'll have an entire class of children from wealthy homes who can be universally identified by their blond hair, blue eyes, tall stature, athletic bodies, and honor roll status. And oh yes, they will all be straight.
Would I do this if I were black and living in America? Shades of Imitation of Life?
Will we then have genetic class instead of economic? Will people who cannot afford genetic modification have children relegated to lower status? Or will the genetically unmodified have the last laugh and become the Morlocks to the modified's Eloi?