Interesting. My father and I had this discussion many times. I recall him arguing his case that sexual orientation was a choice by quoting an article by Billy Graham. I allowed him his argument that it was a choice each of us make.

So I asked him, "Dad, so tell me exactly when you decided to be heterosexual?" He sat there for a long time and realized he never actually considered any other option. Like me, he too was aways hetero. I suggested to him that it was no different from homosexuals either. You just are what you are. You don't actually make a choice about the matter.

A second discussion, relevent to this, was a disucssion I had with a Buddhist Priest in a tent in the heart of Mongolia. His partner was gay and he was gay. I asked him if... him being gay had any negative influence on the tribe there that followed his advice. He answered with this:

Human souls are incarnated 1000s of times. Some choose to be female. Some choose to be male. If you happen to choose to be female (as an example) 90% of you incarnations and then for balance decide "this time" to be a male... well your experience, your soul resume, is all in a female sway. That is what you would arrive as. So your sway, even though you might have a male body, would still be female. This could be an overwhelming desire (sway) that causes your orientation to sway or it could be very confusing to exist in the society where you reside.

...my two cents.