I agree with what you've written.
Now, I'm certainly not claiming this is ALWAYS a choice or however you interpret the statement that "it isn't always nature"... but the correlation to being sexually abused or having a poor relationship with parents is one such conundrum for those that wish to claim it is 100% a born trait.
Again, I don't know what role nature plays versus nurture. My strongest opinion would be that I don't think it's necessarily important why someone is gay. I think someone could argue that sexual abuse and poor parental relationships aren't choices a child makes. And my experiences are obviously anecdotal, but most gay people I know haven't talked about being sexually abused. Many have great relationships with their parents.