There are far far far too many homosexuals for homosexuality to be a "defect", if it does have some genetic basis those genes must be or have been selected for.Now, the thing is,It could be that being gay is a genetic defect, as an organism's sole goal in the long run is to produce enough offspring that it passes its genes along to the next generation of that organism's species.
This admitedly seems sometwhat counter intuitive homosexuality being an evolutionary dead end, but the current explanation is that in certain situations the same genes offer benefits namely greater social compatibility, so having some or all of the "gay genes" in certain cirumstances means you are more likely to pass on your genes.