Incest and homosexuality are both sins. Not one of them should be legalized, although both are pretty much the same thing. Both can affect children, both will force it on to children, and both are capable of destroying our society. If you legalize one, then sooner or later you’ll be legalizing the other, and then you won’t have to wait for long until marriage becomes a mere formality. What will come next? Bestiality? Pedophilia? The Apocalypse?
I'll assume here that "homosexuality" means homosexual behavior, in which case I do believe they are analogous, and I also believe that both homosexuality and incest should be legalized. As long as all involved parties are over the age of consent (i.E. It's not pederasty) and do in fact give consent (i.E. It's not rape), I see no reason to prevent either of these activities. Everyone involved knows what they're doing and wants to do it. If two adults want to have sex with each other, it's not the government's business to stop them on the grounds of being the wrong gender or being too closely related.
Why is incest illegal? There has been compelling and proven evidence that the progeny of incest do have birth defects. Moreover, it is commonly seen as socially repugnant in most cultures in North America.
Now my point, what about recreational incest that does not involve procreation. Is this wrong? There is no damage, or even a risk of harm being done to anyone. Furthermore, consider homosexual incest, where there is axiomatically no chance of producing offspring. There is no harm involved in this.
With regards to society's view on incest being frowned upon, let us consider other opinions society has held that has been morphed over the past two-hundred years. Slavery and black rights, aboriginal rights, women's rights, rights to sexual orientation, and more. Society's opinion should hold little weight when considering why incest is illegal.
If sex isn't just about pushing out babies then it seems logical to me that anything between consenting adults is ok so long as it does no harm to third parties. I suppose someone might say that with incest there is a chance of genetic defects, but this is a dangerous road to take. If the risk of genetic defects means people can't have sex then we must consider there are a number of people in society who have known genetic defects that might be passed on to their children. Should they not be allowed to have sex also?
Both incest and homosexuality are argued for according to some of the same logic: two people "love" each other, and it doesn't affect anyone else, so why shouldn't they be allowed to do whatever rocks their boat? While I do not agree with this argument, it reflects some of the important similarities that the two "sexual" activities have to one another. They are both between "consenting" adults (at least in the relevant sense), they are both supposedly "private," and they both involve "love" (whatever that means here). While the two are not the same in every way, the similarities outweigh the differences.
Children are expected to grow into adults, get married and / or have sexual relationships, but have no idea on how to do things and how to enjoy sex. Dating is awkward enough. Modeling the behavior works best! What better way for it to happen than for it to be in the protected space of the home. Many primitive cultures do it as a right of passage. Western cultures are generally overly puritanical.
Every time I ask people what is the criteria to be able to marry, they respond with "2 consenting adults". Then I respond with "According to your criteria, you have 2 adults, a brother and sister, agreeing to get married to each other" They respond with 3 objections which can be used against same-sex marriage. They say " that is weird" or "that is nasty" or that is morally unaccepted and they shouldn't do that" These 3 can be used against same-sex marriage. One objection that is unique is the retardation of the child. Then I respond with contraception. One Atheist said "wow I never thought about that." I made it simple for him and I made it simple for all of you.
From a secular standpoint, your basis on morals is purely subjective/objective.
So why oppose homosexuality? Why oppose incest? It is difficult to condemn either one from an objective standpoint.
In all reality, Yahweh defines morals, right and wrong, blessings and curses, righteousness and lawlessness, through his commandments. Morality is absolute.
Legalizing incest is not analogous to legalizing homosexuality. In fact, is it possible to "legalize" a sexual orientation? Is it legal to be straight? These questions pose individual debates for themselves. Incest does not have explicit ties to homosexuality, and homosexuality is not explicitly practiced in incest. Incest can indicate any sexual relationship present between siblings; boy and girl, boy and boy, or girl and girl.
I do not think that all homosexuals are incessant and therefore should be treated as a separate category than incest. Although I am personally against both, I do believe Incest to be worse and more serious than homosexuality and so should not be considered similar to each other. However, I do not agree on either of them being legal.
Homosexuality is not "forced upon children". Actually, one could say the opposite by reading these comments : it is heterosexuality that is deemed the only right sexual orientation. Seeing the active reprobation of homosexuality made further up, it is a wonder how it still exists to this day.
Furthermore, sexual orientation is not chosen by anyone, and is a characteristic, unlike incest which is an act which requires -at least- a willing person and is a reprehensible deed.