The liberal movement started positing the "sexual attraction is genetic" argument when they wanted to move the homosexuality debate out of the realm of imminently regulatable human choice and into the realm of non-regulatable human rights. They've been searching for a gene for some time now...mind you, this is a gene that is destined to remove itself from the gene pool every generation because it selects against sexual reproduction (the single most fatal flaw to any gene), so it is unlikely to be handed down from generation to generation, so it must be a very common mutation, happening all the time in every generation by chance. This could be, of course. But it is not science to believe that...it is hopeful thinking at best.
There could be sociological factors at play. There could be other factors. In the end, our brains are biological, so any choice we make is biological, but that doesn't mean our choices are genetically coded.