SSM Plebiscite

[mateinone]

Genetically, the adverse effects are well understood which is one reason why the practice isn't adopted in any culture which comes to mind.

Hmm, so you realise that within Australia relationships between cousins, between aunts/uncles with nieces/nephews can in fact end in marriage right?
It is also legal in every country in Europe and around 1/2 of the USA.
Not only that, but a relationship between say an Aunt/Nephew would see the same amount of shared DNA as that between a Grandparent and Grandchild or that of half-siblings. Yet a relationship between aunt and uncle is the only legal relationship there.

Not only that.. But it is far more likely that someone with Down Syndrome will have a child Down Syndrome.
There are many other genetic defects that are genetic and have a higher likelihood of being passed down to offspring.

So again, I believe it is much more around what we consider acceptable, because surely no one is suggesting that people should be screened for the possibility of passing on genetic defects. That would seem a little Orwellian.

Also, what about when someone is infertile, should they then be able to marry a sibling?

As for historically, there is considerable data showing historical relationships between relatives.
Cleopatra married not 1, but 2 of her siblings.
Most of Europe was ruled by marrying cousins for about 200 years.

See I believe it is okay to say that the reason why there shouldn't be incestuous relationships is that I don't believe it is "right" or I consider it "wrong".
Based on what I have learned throughout life, it makes me feel "ewww". I know that isn't scientific and I am okay with that.
I pass that judgment. I don't think that is a good reason for the law to change or stay the same, because it is nothing more than how it makes me feel.
I don't apologise for feeling that way either.

AND that is the crux.
People can feel that same sex marriage is wrong and contrary to their beliefs, based on their upbringing.
But that shouldn't impact the law.