It is interesting - at this point the conservatives seem to want to argue that homosexuality is chosen and/or environmental while the liberals argue that is genetic or predetermined, so to speak. You make a good point, orientation and behavior are two different concepts. We can be attracted to all sorts of people, objects, whatever, but that doesn't mean we have to act on it. Hence, I think behavior almost always is a choice. Sexual orientation? At this point is appears to be both biological and environmental. One common misconception that people have is that if a trait or characteristic is determined by an experience or the environment it is easier to change. This is not necessarily true. We are born with somewhat undeveloped brains and our brains continue to develop via interaction with the environment. Therefore, early experiences can shape our brains in ways that very difficult to change later on. Perhaps children are born with a genetic predisposition toward homosexuality and then some critical childhood experiences (or lack thereof) lead to expression of this predisposition. One interesting line of research would involve studying those with the "genetic predisposition" who become heterosexual in orientation. Are there certain childhood experiences that may prevent homosexual orientation among vulnerable children?
Interesting point indeed. A parallel line of inquiry has focussed on the question of "resilience" in people who, as children, experienced all manner of trauma and deprivation yet who overcame what would have appeared to be insurmountable obstacles and made a success of their lives.