First, I have decided to not incorporate homosexuality into my opinion. There is too much that can be argued with the subject and I want to keep the question in which it was presented. However wrong I am to the truth, I apologize and will keep an open eye when new scientific research has been developed.
I believe that people do not initially "choose" the sex that they are attracted to. The hormones and chemicals in one's body do the deciding for them. For instance, I am attracted to men. I did not say, 'Yes, I choose to be attracted to men'. Rather, it was the hormones in my body that gives me the feelings of likeness towards men. I can look at women and not get the same feelings as I might, say if I looked at men in the same manner. It is the way that we reciprocate the feelings of lust and the like towards the sexes, and we do not contol our body's chemistry.
Nevertheless, I understand that there are ways in which one may become conditioned to certain aspects of life, "learned helplessness" as one example. But to how far this concept goes into relationships between the sexes is another question, and a question that people are still trying to make clear.