How do you know? You admitted yourself that you didn't read it, so you have no idea what the selection criteria or methodology was. There are also other studies that show a range of heritabilities of homosexuality. Did you bother searching for them? If you have no problem with gays, why are you so eager to instantly dismiss the evidence out there without even looking at it first?
Here is where you show your ignorance of genetics. There is no single "gay gene", that's been obvious for a long time, since homosexuals and their offspring do not display simple Mendelian inheritance.
That doesn't mean it isn't genetic though. There is no single "hair color gene" either - do you deny that hair color is genetically determined? Do the terms "incomplete penetrance" or "blended inheritance" mean anything to you? If not, you have no idea what you are even asking for.