Again, though, that is neither here nor there in respects to this argument; though I believe you are implying that, in humans, homosexuality is an exclusively higher cognitive choice. To that end, higher executive function only serves to initiate final decisions re: biological imperatives, and subsequently place them within a social context; animal or human, this homosexual tendency exists for a specific biological purpose - reason notwithstanding.
At any rate B, I feel this is nothing more than a Red Herring, relative to the true point at hand: homosexuality and homoeroticism are ubiquitous natural tendencies; and so, the biological argument is removed as a crux-point for the homosexual discourse as a whole. The group(s) opposed to homosexuality often use "A man and a woman is natural, that's how anatomy works" as a talking point. They use it, of course, because biology is a far more legitimate and rational explanation than, say, moral reasoning. What we have left, then, is a much more honest discourse between those who find homosexuality to be morally acceptable, and those that do not, with nothing more than morality as the reasoning.
Higher human function and so forth have little-to-nothing to do with the point at hand! Back to the eating example: you can choose what type of food to put in your mouth, but not the desire and necessity to eat it - and so, to imply sexuality is any different is logically inconsistent. Certain imperatives are inherently beyond the control of rational choice, with homosexuality being one of them.
I feel you are drawing conclusions from premises never presented to you, D. The argument is not, "Animals do it, and so should we", but rather: "It is a natural phenomenon, so the point that it is unnatural must logically be removed from the discourse". Nobody is drawing the conclusion you are, insofar as equating this biological phenomenon with morality. When speaking about biology, I feel it is amiss to begin adding in words such as "right" and "should", because you are projecting a human construct onto an evolutionary phenomenon. In the context of animal-kingdom-wide homosexuality, there is only "it does happen", and not "this means it always should". Again, the point here is that this and other mounting [no punt intended] evidence seem to suggest that, contrary to the suggestions of those that are opposed to it, homosexuality is an inherently natural phenomenon. As I said to B, the only argument then remaining is morality, which is necessarily less attractive to an individual opposed to something, as it is less justifiable.
In simple terms, AE14's evidence removes the ability to say, "Homosexuality is not natural, and therefore should not happen". All the opposition is left with is, "Homosexuality is against my beliefs, and therefore should not happen".
