I've heard three arguments to justify why homosexuality is not a disorder of 'natural' sexuality: It is perceived as 'natural for them' by some people; homosexual sex is consensual and not harmful or abusive; and animals have been observed engaging in homosexual sex.
None of these arguments convinces me since it seems to me that: everyone's sexual desires appear as natural for them (however weird or extreme they might be); consent and lack of abuse don't equate to 'natural'; and what some animals sometimes do could also be a disorder of their natural behaviour.
What are the other arguments about the naturalness of homosexuality? What about the argument that male and female are naturally 'complementary' - physically, psychologically and sociologically?
Perhaps the first question worth answering would be what one means here by "natural". What is "natural" can be opposed to many different things: "artificial" might be one, for example, but that doesn't seem to be quite what one has in mind when one asks whether homosexuality is "natural". Indeed, I'm inclined to think you don't know very well yourself what you mean by the word: hence all the "scare quotes". Another question is why it should matter. If homosexuality is not "natural", does that mean it must be wrong? One might well suggest, and it has indeed been suggested, that sex with birth control is not "natural" either, but, despite the wel-known views of some, many of us wouldn't infer anything about the moral status of such expressions of sexuality from the fact, even if it is one, that it is not "natural". And sure, there are plenty of senses in which men and women are "complementary". Among them, the obvious one is that it takes a man and a woman to make a child. But it's hard to see what's...