uh, homosexual behavior is found in a wide variety of animal species. if it were a "disorder," it would have already been selected against. your analysis is just overly simplistic - there are a lot of traits that confer advantage to a group while reducing reproduction by an individual.
Sure, that's a valid point. But another valid point is the causative agent for homosexuality in humans is the same causative agent for homosexuality in animals and this would invalidate your point if it were true.
Anecdotally, and this is sort of a alternative guess. Within a population of equal size, much more humans will be homosexual than animals. I mean gay people are really abundant but I can't say the same for gay lions in Africa.
