Well I hope it's not
only sexuality that shows that we're not machines!
(And
you should know better Anny... you must have seen the
All Is Full of Love video!)
Apart from that, frankly, I don't even understand what it
means to say that homosexuality is "unnatural".
Does it mean that there is no homosexual behaviour in nature? If so, the idea is just wrong. There are lots of homosexual behaviour amongst animals. And, even more obviously, human beings too are natural creatures, and some of them are homosexuals. They don’t seem to be less natural than anybody else. There may be more hetero- than homosexuals, all right. And? There are more right-handed than left-handed people too. Does that make being left-handed "unnatural"?
Does it mean that homosexuality seems to be "useless" from the point of view of the reproduction of the human species? If so, it certainly is. But then, millions of other things that human beings do aren’t useful to that goal either, many of them are even downright harmful. What about smoking - kills you, kills other people, harms your offspring. Does that make smoking therefore "unnatural"?
Or does it mean that homosexuality should be morally deplored because it is useless seen from the point of view of reproduction? If so, that idea is just wrong. There isn't anything more stupid, dangerous and inhuman than to try and derive morals and norms from "nature" (as Kolya said). If we want to know whether something is right or wrong, why should we even consider whether "animals do it too"?! Some of the very best things that humans do are things that have no parallel at all in nature. Letting your offspring die or killing it if it was born prematurely is natural. That's what animals do. So is it morally good therefore? Bullshit!
What matters is: Does something make people happy or unhappy? Does it make them free or unfree? Does it make our society just or unjust? Does it make our way of life richer or poorer? These things have nothing to do with biological survival. They don’t concern life as such, but a good life. A human life.