Thank you for this thread; the debate over "is it a choice" is actually one of my pet peeves, as a non-LGBT-person who follows the discussion. I understand that "it's a choice" is an erraneous argument, but it seems to get a disproportionate amount of focus.
If homosexual behavior is acceptable (which it is in all our minds), like being left-handed, what does it matter if the tendency is a choice or not? Either way, it's none of anyone else's business.
If homosexual behavior was unacceptable (which it is in the minds of anti-gay-advocates), like psychopaths abusing other people, what does it matter if the tendency is a choice or not? Either way, we should do everything in our power to discourage it.
There are also people at the non-extremes of the heterosexual-homosexual-spectrum, whose orientation is more fluid and who may actually make a choice to limit their options. Granted, it's probably always a choice to "be" heterosexual, but a choice nonetheless.
I'd just prefer
more a focus on "ok to be gay" and less on "not a choice".
Edit: I did mention it was a pet peeve... so I draw this Venn diagram, and only after I was done with it realized that it would be better as a Fourfold. Doh. At least it's sort of pretty and colourful.