Finally, I advise you to bait him into admitting that there is no good reason to prohibit homosexuality,
I know of no movement abroad that proposes the prohibition of homosexuality, whatever that might entail.
and that, in fact, the only reason he thinks it *should* be prohibited is "because Heavenly Father said so."
Which is, given the source (Heavenly Father), a perfectly good reason to oppose homosexuality in its own right. However, since Scratch does not believe in Heavenly Father or his authority, all is moot.
So, while your remarks concerning religion and etc. *do* seem somewhat off-topic and tangential, you're basically right. It does not matter what gay advocates say, or what scientists turn up concerning the "causes" of homosexuality, or whether it is a choice, or whether it is genetic, or what.
1. The brain sciences have "turned up" precisely nothing regarding the "causes" of homosexuality. They have turned up pretty much what they have turned up in other areas, such as the addictions: there are predispositions and biases, of subtle conplexity, that have a genetic or biological origin. The political weight of such knowledge is exactly zero.
2. Gay advocates have no better knowledge then such scientists, and, of course, have a vested interest in promoting the biological determinist argument as this best serves the cause of identity politics and the cult of victimology that is its continuing nuclear option in our present political climate.
For "Droopy" and his ilk, it is all a matter of nitpicking the details, which, in the end, he shouldn't care about, since Heavenly Father said so, end of story. I daresay that his focus on the minutia is evidence that he doesn't want to confront the truth about his position, which is that it is based purely in faith and metaphysics, rather than real, empirical evidence and logic.
Faith in the rightness of homosexual behavior and its culture is as much metaphysical as any other form of "faith" (not understood in an a strictly LDS sense, obviously). Science, again, has nothing to say regarding the origins of homosexuality as to its "cause" any more than it has much to say about the origins of musical or mechanical aptitudes, or why one person gravitates to one religion, one to another, or one leans to the left or to the right politically.
Scatch, likes the namesake of his screen name, and like so many others who follow him, is really afraid of free agency. The rage for genetic determinism has a long pedigree, and is simply the most recent manifestation of the perennial effort to deligitimize the concept of choice and place much of our behavior outside the boundaries of individual volition.
Monson is right. Sin wears the mask of tolerance, but, one might add, tolerance dances to the tune of determinism. What is determined and beyond human control cannot be judged. It cannot be critiqued or analyzed, and no discriminations or judgments can be made, in an ethical or moral context.
Its all so convenient, really.