How do I distinguish between nature & choice?

The essence of this question can be restated in one or both of the following forms:

a) What is the dividing line between philosophy and the special sciences?

b) What is the difference between philosophy and religion?

Regarding (a): is the question of whether or not one's "sexual orientation" might be open to one's power of choice primarily a philosophical issue, or an issue for the special sciences? To my knowledge, Objectivism has never claimed that sexual orientation is a philosophical question answerable by Objectivist philosophy. It is an issue for the special sciences to investigate and resolve, following broad guidelines of rationality, logic, and so on, including valid concept formation, as identified by philosophy.

Regarding (b), adherents of religion might ask: But isn't philosophy supposed to be an alternative to religion, and don't most religions endeavor to prescribe every detail of people's lives? Why wouldn't philosophy need to do that, too? Isn't philosophy nothing but a form of religion in which the beliefes in which one has faith emanate from within man's own mind rather than being instilled in man by some external authority residing in another dimension of reality?

The topic of "Philosophy" in The Ayn Rand Lexicon succinctly summarizes the essence of what philosophy is (and isn't). The second excerpt in that topic explains:

Philosophy is the science that studies the fundamental aspects of the nature of existence. The task of philosophy is to provide man with a comprehensive view of life. This view serves as a base, a frame of reference, for all his actions, mental or physical, psychological or existential. This view tells him the nature of the universe with which he has to deal (metaphysics); the means by which he is to deal with it, i.e., the means of acquiring knowledge (epistemology); the standards by which he is to choose his goals and values, in regard to his own life and character (ethics)—and in regard to society (politics); the means of concretizing this view is given to him by esthetics.

This excerpt differentiates philosophy from both religion and the special sciences. Unlike the special sciences, philosophy is concerned only with the fundamental aspects of existence. And, unlike religion, philosophy is concerned only with existence (including identity and consciousness as corollaries of existence), not with some alleged additional "spiritual dimension" of reality apart from existence (existence as known to man by sense-perception and conceptual integration of sensory-perceptual material).

As against religion, Objectivism strives to be a rational philosophy based on reality and reason. As against the special sciences, Objectivism strives to deal with the fundamental aspects of existence, not with all the specific details that may require considerable advanced scientific inquiry to resolve fully and objectively.

Perhaps the questioner is only trying to ask: what do Objectivists generally see as the current state of the evidence? If homosexuality is just a "developmental abnormality" (as one Objectivist psychologist once described it), might it then be possible for the special sciences to devise ways of changing the course of development by means of intervening therapy of some kind at a young age, in the early stages of the "developmental process"? If that is what the questioner is asking, the answer will need to come from experts in that field. There is no way to arrive at an objective answer by reasoning from purely Objectivist principles.

Again, religious adherents might respond (reflexively, perhaps): but isn't this kind of issue far too urgent and pressing to leave to scientific research and analysis? An Objectivist can answer by offering some important but very broad principles concerning the initiation of physical force, beyond which people need to be free to live their own lives as they so choose, including the freedom not to deal with homosexuals if they find homosexuality repulsive (morally disvaluing) on the basis of the evidence that they are aware of -- and, likewise, the freedom of homosexuals to pursue their sexual orientation as they see fit, so long as they respect individual rights.

Update: Some Clarifications

Some of the comments, and an update by the questioner, have sought clarification of the following formulation:

To my knowledge, Objectivism has never claimed that sexual orientation is a philosophical question answerable by Objectivist philosophy. It is an issue for the special sciences to investigate and resolve,

The "question" I am referring to is whether or not one's sexual orientation is under one's power of choice, not necessarily directly, but over time through automatization -- like any other subconsciously entrenched, habitual pattern of choices and actions graudally automatized through repetition over time. If it is, then there are, indeed, a great many implications, as with any other category of response that is produced by automatized preferences.

Also, by "Objectivism" I mean the philosophy of Ayn Rand and its supporting "literature" in the works of Ayn Rand and others who were closely affiliated with her and endorsed by her (such as Leonard Peikoff, in particular).

I've seen others at times refer to remarks by Ayn Rand condemning homosexuality in at least one of her answers in Q and A sessions following one or more of her lectures, but as far as I can discern, none of those specific remarks made it into the book, Ayn Rand Answers. One comment by her on a related issue that did get included in that book is the following (p. 139):

[Questioner:] Will you comment on what makes the male the dominant sex?

[AR:] No, because I would have to discuss the psychology of the sexual act. That's a proper subject for doctors and psychologists, but the psychology of sex is not my great interst. Try to figure it out.

Also refer to OPAR, Chapter 9, "Happiness," subsection titled, "Sex as Metaphysical", pp. 343-348. On p. 346, OPAR explains:

The subject of sex is complex and belongs largely to the science of psychology. I asked Ayn Rand once what philosophy specifically has to say on the subject. She answered: "It says that sex is good."