Woulfe,
"1. incest is an illegal act, homosexual sex is not"
A. You use the law to bolster your case when it suits you but challenge the law
(marriage is between a man and a woman) when it doesn't.

"2. rights devolve to (or are denied to) human beings, not to acts"
B. Incestuous couples are human beings.

"3. people are not born with a sexual preference for their first-degree relatives (at least, I'm not aware of any research that has revealed such a sexual preference, or any individuals who claim one)"
C. You imply that homosexuals are, which has been thoroughly refuted. Even Peter Tatchell admits this now.
Refer "Gene Genie":
http://www.petertatchell.net/gay%20gene/gene%20genie.htm
Refer also Dr Francis S Collins, former head of the human genome project:
http://www.freerepublic.com/focus/f-news/1801869/posts

"4. Australians who are born with a preference for sexual partners of their own sex constitute a class which is currently denied the right to marry their partner of choice"
D. You use the false "born with a preference" premise discredited in C.

5. following from 3, there is not a class of incestuously oriented people to grant (or deny) rights to, in the same way there are classes of left-handed people, indigenous people, and homosexuals.
E. Following from C, your statement has no validity. Indigenous people cannot change their race which they genetically inherited but homosexuals can change their sexual orientation (refer below) which they did not genetically inherit.

"While many mental health care providers and professional associations have expressed considerable skepticism that sexual orientation could be changed with psychotherapy and also assumed that therapeutic attempts at reorientation would produce harm, recent empirical evidence demonstrates that homosexual orientation can indeed be therapeutically changed in motivated clients, and that reorientation therapies do not produce emotional harm when attempted"
Essential Psychopathology and Its Treatment,
Jerrold S. Maxmen & Nicholas G. Ward, 2009 edn,
W.W. Norton & Company, p. 488

At the risk of being drawn into a prolonged discussion..

KMB, C has not been "thoroughly refuted" at all. There are many more theories on the biological basis of sexual orientation than heritable genetic control. I would agree that inherited genetic orientation (the "gay gene") is highly unlikely, but a biological basis for phenomena such as brain feminisation and sexual orientation and behaviour is still yet to be properly investigated (eg brain structure, neurohormonal influences etc). The major problem lies in measuring such things as hormonal changes in the womb (or indeed a combination of any number of factors such as diet, lifestyle factors etc) and following them through to a measurement of sexual orientation in adult individuals.

As for "homosexual orientation can indeed be therapeutically changed in motivated clients", yes I believe this could possibly be the case as human beings are strange creatures and can override instinctual behaviours consciously. For example, while born with survival instincts and a predilection for self preservation, can be convinced to go to war or to strap a high explosive device to themselves and kill themselves for no good reason other than a promise of an unknown afterlife.

"3. people are not born with a sexual preference for their first-degree relatives (at least, I'm not aware of any research that has revealed such a sexual preference, or any individuals who claim one)"
C. You imply that homosexuals are, which has been thoroughly refuted. Even Peter Tatchell admits this now.
Refer "Gene Genie":
Refer also Dr Francis S Collins, former head of the human genome project

"4. Australians who are born with a preference for sexual partners of their own sex constitute a class which is currently denied the right to marry their partner of choice"
D. You use the false "born with a preference" premise discredited in C.

Not discredited at all, we are psychologically born with our sexual preferences, as with all aspects of life, they are in varying degree's. If you read all of Peter Tachell, you will find he agrees.

Francis S Collins, is a right wing christian creationist and must deny anything not fitting into his demands. So you couldn't believe anything he says on this subject.

This is a moral issue, nothing else. It's nothing to do with biology or physiology it revolves around moral stances, every culture and society has morals it enforces to maintain control and in every culture they are different. Ethically speaking there's nothing wrong with homosexual or incestuous mating, it's seen throughout nature, again in varying degrees. You also see it deeply entrenched within all religions, only mating with those of the same belief, church, culture, tribe, town, region, state, country or a distant relative.

If you have an ideological agenda, you can look at it any way you like, but it doesn't make you right in the eyes of natural reality. Just biased, discriminatory and prejudiced.

KMB, Why do you have such an obscession with incest?

KMB,

The theory that people are born homosexual has not been discredited.

As realisation of sexuality does not generally surface until the early teens, it is difficult to determine whether it is congential or environmental.

However, if it were environmental, therapy would have a reasonable chance of success to "cure". As therapy has very little success, there is a strong inference that it is congential.

However, as there has not been found any one smoking gun the debate is still open.

The single feature that by the teens the sexuality is pretty much permanent, and as such the definition of your sexuality should not have any bearing on your rights as a human being any more than if you were missing a leg.

Anyone who discriminates on race or gender is a bigot.

When talking about civil rights, it must be easy to confuse a right with a licence, because it seems to happen very often. In the golf club example, the rights extend only to equal access to membership, to getting in the front door, if you like. I can't be prevented from joining the golf club because I am homosexual, but the club will not grant me a licence to use its facilities unless I can meet its legally permitted conditions of membership, such as membership fees, code of conduct, residence restrictions, etc.

In the case of marriage, I am 'stopped at the door.' Opposite-sex couples have the opportunity to show that they meet the conditions for marriage: giving notice, paying fees, nominating an authorised celebrant: http://www.ag.gov.au/www/agd/agd.nsf/Page/MarriageGetting_Married However since 2004, the federal government has discriminated against me in a way that is illegal for any other non-religious organisation (except in Tasmania http://onlineopinion.com.au/view.asp?article=8656 ).

Marriage was not officially defined in Australia until 2004, when, under pressure from the Christian right, the government inserted the current sex-based definition: http://www.smh.com.au/articles/2004/05/27/1085461876842.html I’m not so much challenging a law as seeking to restore the damage that was done five years ago.

On sites like narth.com and "Americans for Truth about Homosexuality" http://snipurl.com/gw7v3 there is no shortage of people claiming that (a) homosexuality is a pathology that (b) can be 'cured.' This claim has been dealt with elsewhere (for example http://www.religioustolerance.org/hom_nart.htm ). When claims about the 'curability' of homosexuality are raised in a debate about gay rights, to me the most disturbing aspect is the underlying assumption that it's a justification for denying civil rights to homosexuals. Left-handedness is 'curable', but long ago we realised that the success rate was extremely low and the cost to the individuals concerned was unacceptably high. Obesity is curable, but we don't award civil rights according to Body Mass Index.

Of itself, the homosexuality-is-curable argument is utterly disreputable, but it would be illuminating to hear from the people who use it why they single out homosexuals for the denial of civil rights, while ignoring a host of other 'curable' conditions.