Kyure, I'm afraid you just missed the entire point of his post. In fact, I'm not 100% sure you actually read his post. ggwp
From what I've read, this issue is much more nuanced and convoluted than simply being a multiple choice question that we don't know the answer to ( a.) born gay b.) influenced by environment etc. etc.). The only thing I can really say with any certainty in good conscience is that is most certainly is not a conscious choice.
For example. I like the colour green. Actually, I like the colour green a lot - it's my favourite colour. It's not that I suddenly decided one day that I'd make green my favourite colour... it's something I noticed about myself. It's simply me being cognizant of a preexisting state.
Whiiiiich brings me to the actual discussion at hand. How did that state come to be? Well there's a lot of research on a lot of different sides, and I do think a lot on any side of the issue has some merit. I'll list out a couple of statistics here.
I.) In the case of twins, if one twin is gay there is a 20-50% chance of the other twin being gay. from an article linked in this thread previously.
II.) It is estimated that ~5% of the US population is gay. from very brief searches via google. ~ notates "approximately."
If you look just at I, you'll notice that it isn't 100%. This almost without a doubt shows that DNA isn't the only factor. However, I don't really know a lot about the main subject of the article I pulled that from (linked earlier in the thread) so I'll just leave that in the air. However, If you look at I and II together, you'll notice that 5% isn't included in the range for I. Assuming DNA had nothing to do with sexuality, you should see the range including significantly lower values.
It should be considered that twins would be exposed to much of the same environment growing up, which in all honesty would bump up the chance they both grow up to be homosexual instead of just one, and while I can't say this without falling prey to speculation, I don't know if that would truly, all on its own bump a 5% chance to a 20-50% chance. Although twins and born and raised together at home, nobody can be certain the environment they experience besides that are identical to each other, of how similar their environments are.
Now, I know earlier that I said green is my favourite colour, but there are some honorable mentions. Quite recently, I've taken a very strong liking to the colours purple and pink. which is uh... pretty damn obvious if you /dl and /lp me (Pouffywall) ingame. However, why would my colour preferences change if I were born with them? I mean, I'm almost 17. I'm not developing at the rate kids do, and green has been my favourite colour for my entire life. Why, praytell, would certain shades of pink and purple begin to contest my love for green so late in my life (relatively speaking) if it was so simple as "I was born with it" or "It developed as a small child."
Food for thought.
And in case drawing a parallel between colour preferences and sexuality is offensive and unconvincing to some people, I'm also becoming a lot more liberal in my sexual preferences. Sexuality isn't static.