http://content.gay.com/channels/news/heads/001117_gay_twins.html
There have been several studies of twins, at least one of whom is gay. In each case such as that above, in identical twins (obviously with identical DNA) the probability that the identical twin of a gay person was also gay was 50% or less. If there was a gay gene, the result would have to be 100%.
I'm not sure why your post was directed to me, as I really have no opinion on the subject, other than to say if there is a genetic tendancy (as there is with alcoholism), then it could be overcome.
That said, I do see a flaw in the study you mention, in that it assumes that a "gay gene" would be the dominant factor every time (i.e., the twin would always be gay, too).
If there is a gay gene (if!), I suspect it would work more like the "alcoholic tendancy" gene --- which is present in most every Native American --- in that it gives a person a greater % chance than the overall population at being gay.
For example, if the chances of a non-gene-carrying person being gay was 3%, then the chances of the gene-carrying person being gay would be 5% or somesuch (to use arbitrary figures).
Hence, you would need a study of thousands of twin sets to see if there was a like, ala the studies done on breast cancer in families, etc.
I just doubt the sample size of twins is big enough to get a viable study. (Plus there is the polluting factor of how they were brought up, which could junk the study, too.)
That said, I don't disagree with you that there is not good evidence of a "gay gene." I just don't think the study you cite is reliable.