On the note of sexuality/gender being natural vs. environmental:
I can completely understand that neither has been scientifically proven, as none of the available data can be definitively tethered to something scientific. However, I think it's nearing absurdity to believe that either sexuality or gender identity is anything but natural or genetic (please note I am not saying that there aren't individuals who make the choice against their inclinations, though I believe them to be rare). There are countless examples spanning the entirety of our species' existence that reflect the reality of homosexuality or gender incongruence. It's a static occurrence in every single culture to have ever existed, many times being against the individual's well-being; the evidence to this much is overwhelming.
It is true that there is cultural magnetism to certain habits, but these are very obviously either defined by a society's growth towards comfort (such as with the Greeks, who were not necessarily sexually attracted to the same gender, but saw nothing wrong with providing each other gratification), or by an individual's natural inclination to establish preferences (fetishes, hair color preferences, body preferences, etc.) within their own pre-existing sexual basis, i.e. women, men or both. This same determination occurs for gender expression: an individual has an established identity and their expression of that identity is a reflection of their growth. Of course exposure to one's environment will help shape an individual's growth, as we can only experience what we are exposed to, but it will not define (or redefine) their basis.
If nothing else, I feel the biology view just bleeds both common sense and good will. I am admittedly embarrassed for our species that we cling to dismissive, grasping arguments despite our history screaming otherwise at us.