Acknowledging that some of us have chosen our sexual preferences does not require us to disprove any "gay gene" studies. None of the studies which have gained worldwide attention over the past several decades has even claimed to be able to find biological causes for all queer people's queerness. On the contrary—dozens of studies have found substantial numbers of identical twins who have different sexual preferences, so the very most that any biologists are even hoping to prove is that biology is one of multiple factors that may influence sexual preference. However, the current evidence for even the slightest direct biological influence on sexual preference is extremely shaky at best, and has been ridiculously overhyped by the homo and hetero media alike. (We specify direct biological influence here because everything that people do is "biologically influenced" in the sense that it depends upon the existence of a living, biological human being.)
As you read the critiques of "gay gene" studies on this website and other queer by choice websites, bear in mind that even some of us who consider ourselves queer by choice do believe in some form of the "gay gene" theory—either that some people's queerness is 100% chosen but other people's queerness is 100% biologically determined, or that both choice and biology have some direct influence on all people's queerness. But also bear in mind that some of us reject the "gay gene" theories completely. And no matter what beliefs we as individuals may hold about "gay gene" theories, the media hype about these theories has had a profound impact on the way that all our choices are perceived.