The initial research was done many years ago so this already came up and was discussed by Christian fundamentalists*. Google found me a response to the research that I suspect is representative. Note that the article is from 2010.
Quote:
The case for a ?homosexual gene? has evaporated, but let?s say that researchers really were able to identify such a gene. After all, mutations in a cursed, fallen world can cause all sorts of abnormalities and malfunctions. For one thing, that would be a result of the Curse, not creation. And would knowledge of such a gene make right what Scripture clearly says is wrong? Absolute right and wrong exist independent of any secondary causative agencies.
This was a reaction to the initial research, which wasn't overly convincing. Thus the first sentence. The rest of the paragraph makes a good argument for why it would not be acceptable even if genetic. Note that when I say "good", that does not mean I agree with it (I don't). It means that I think it would be convincing for the faithful. It accepts the validity of the science (so can't be counter-argued with "science proves....") while rejecting the implications.
*You did specify "fundamentalist" which is why I'm going with this rather than Kraichgauer's more accepting reply.