It's definitely by choice. The gay gene would kill humanity.
So, you're actually born straight as an arrow

You should be proud :D
The addition of excessive emoticons can be inferred as a tacit admission of insincerity or satire. However, despite what your honest opinion may or may not be, I will still give a retort (if not for the reason to address those who do hold these notions, than at least for the sake of merely seizing an opportunity to be argumentative and hear myself talk).
Anyway:
That is a terribly flawed argument, as it is patently founded on an unusually large absense of correct understanding of even introductory-level evolutionary biology.
One ought to be able to intuit most of this by pure reason alone. Nonetheless, people are exceptionally gifted at being stupid.
Using your logic, we can conclude that infants born with severe birth defects choose it so, as they have less than the standard degree of reproductive success required for the existence of our species. Surely, any genotype presenting a deviation from the norm of the phenotype is a choice, no? No--indubitably no.
Organisms get snuffed out or born congenitally unproductive all the time due to lack of fitness. But the fitness of the organism is of no significance. The individual is irrelevant in the process of evolution; only the overall condition and overall fitness of the species is of any consequence in the course of evolution.
Moreover, evolution is reliant upon these individual deviations, as they are (simply put) one of the mechanisms through which the individual, and thence the species, increases fitness—via mutations that benefit the species, like tails or claws or camouflage.
The downside of this is obvious: not every mutation or deviation will be beneficial, and most will actually decrease the fitness of the organism, and occasionally that of the whole species (if, say, the rate of environmental evolution outpaces the rate of biological evolution, and the species becomes moribund or even goes extinct for having not adapted fast enough, to give but one example). That is an ineluctable sequela of some evolutionary processes.
But to reiterate my point, the organism is expendable and nugatory. All that matters is the species. That is to say, the genotype does not import; rather, the phenotype is what matters and this is one of a few determinative factors in the evolutionary trajectory and proliferation or annihilation of the species.
Organismic foibles or genomic glitches are not volitive, but involuntary.
Looked at from another perspective, the individual may reasonably be conceived of as an impotent system of an exiguous, piddling nothing that fluked itself into existence as an element of a much larger and less meaningless system of a set of intraspecific individuals. A set which is itself a mere particle within the immensely more significant and incalculably larger biological universe, whose orders are to weed out all non-hackers who do not pack the gear to survive in its beloved biosphere (FMJ allusion).