> I assume you're married to a woman (or a man, if you're a woman) because you responded negatively to a comment that said voting for prop 8 wasn't an action that was harmful to gay people.

I didn't respond negatively to that comment. I provided an explanation, that those people who object to the idea of gay marriage do the same thing as almost everyone else, even many who are in favor of gay marriage: They have a certain image or ideal in their head, of how a marriage has to look like, and everything that doesn't fit that image feels wrong to them and shouldn't be legal. Hence almost everyone wants to exclude certain types of relationships from getting married.

I explicitly focused on that argument:

> They very explicitly wanted to take a right away from other people, even though they suffered no plausible harm from those people exercising that right.

from the comment, which IMHO is a misleading argument, since I don't believe that many gay marriage supporters take it seriously. So you should finally answer my question, so I know where you stand: Do you believe that that argument is valid, i.e. are you also fine with a mother (50) marrying her son (30) or 12 people getting married? According to that argument it should be legal as well, since they don't harm anyone, but I have a strong feeling that even most gay marriage proponents wouldn't support such a type of marriage. So they're line would just be somewhere else.

The paper already starts of with multiple premises that don't apply to any of my arguments.

1. I never put forward an argument against gay marriage, yet the paper is all about debunking arguments against gay marriage.

2. I don't consider it a bad effect if other types relationships were allowed to get married, it's the opposite, I'd consider it a huge improvement to what we have right now. Yet the paper assumes someone said: "If we allow gay marriage, we will also have to allow [policy X], which would unquestionably be bad."

Hence I must assume, that you either didn't read or understand anything I wrote, or you didn't read the paper.

Your argument was that everyone believes that marriage should be restricted in some ways, so that believing it should be restricted to opposite sex couples is no worse than believing it should be restricted in any other way. If you read it, the paper addresses that kind of slippery slope argument. It explains that it is not at all difficult to find good reasons for expanding marriage to include same sex couples without expanding it in every other conceivable way. Hence, there is no prima facie case to be made that every other still-existing restriction is a violation of anyone's rights.

> Your argument was that everyone believes that marriage should be restricted in some ways, so that believing it should be restricted to opposite sex couples is no worse than believing it should be restricted in any other way.

No, my point is that if someone brings forward the argument that same-sex marriage is fine because it doesn't harm anyone, but they then oppose other types of marriages that don't harm anyone, they obviously don't take their own argument seriously. Hence they shouldn't be surprised if others don't take it seriously as well, but they actually criticize them for doing so.

> It explains that it is not at all difficult to find good reasons for expanding marriage to include same sex couples without expanding it in every other conceivable way.

Which is completely irrelevant to this discussion, because the reason that was brought forward for expanding marriage was "it's fine if it does no harm to anyone", not some other reasons which prevent a slippery slope.

You're basically saying, that if the other user had brought up a better argument, my critique wouldn't apply.

Edit: But just out of curiosity, what argument would logically allow a same-sex marriage of men or women, who aren't closely related to each other, but exclude two brothers or sisters from marrying each other?

What the OP actually said is the following: "They [prop 8 supporters] very explicitly wanted to take a right away from other people, even though they suffered no plausible harm from those people exercising that right."

This isn't presented as an argument for the legality of gay marriage; rather, it already presupposes that gay couples have the legal right to get married (as indeed they did in California before proposition 8 passed). It's uncharitable and implausible to assume that the OP would be able to present no argument for the legalisation of gay marriage other than "it wouldn't harm anyone". It certainly doesn't advance the discussion to attribute to them a weak argument that they didn't even make.

>But just out of curiosity, what argument would logically allow a same-sex marriage of men or women, who aren't closely related to each other, but exclude two brothers or sisters from marrying each other?

What argument would logically allow an opposite sex marriage of a man and a woman who aren't clearly related to each other but exclude brothers or sisters from marrying each other? Unless you think that there's some kind of analogy between same sex relationships and incest, then same sex marriage is totally irrelevant here. Can't think of a reason to ban incestuous marriages? Then the slippery slope starts from opposite sex marriage, not from same sex marriage.

Why do you avoid my answering my question?

> What argument would logically allow an opposite sex marriage of a man and a woman who aren't clearly related to each other but exclude brothers or sisters from marrying each other?

I can't think of one, which is why I never claimed there are good reasons to not allow such type of marriages, unlike you. I said multiple times that I'm completely fine with all types of marriages and relationships that don't exploit or harm people.

> Can't think of a reason to ban incestuous marriages? Then the slippery slope starts from opposite sex marriage, not from same sex marriage.

Yes, which is why I'd allow such type marriages. You however claimed there are good reasons that the slippery slope either stops after same-sex marriage or doesn't even start in the first place. So would you just answer my question and give me one of those good reasons, why for example sibling marriages are bad and normal same sex marriages are fine?

As far as I can tell, you want to make some kind of false equivalence between gay people who are opposed to incestuous marriages and straight people who are opposed to gay marriage.

I hesitate to engage because anyone who does this is unlikely to be interested in having a serious discussion. But here's a point you might have missed. Over the past hundred years or so, there has been a huge shift in the perception of the rigidity of gender roles. The expansion of the legal definition of marriage to include same gender couples is a logical continuation of this trend. If men and women are fundamentally equal, it's hard to justify gender restrictions on marriage. In contrast, attitudes to incest have not shifted much at all. Indeed, if anything, cousin marriages are less socially acceptable than they were previously. Why is this? I think the answer is obvious. People have seen many examples of normal, successful, non-abusive long term gay relationships. But they have not seen similar evidence in the case of incestuous relationships.

This being said, I think you'll find that most people don't actually care very much whether incestuous marriages are legal. And indeed, around the world, the extent to which incest is legally prohibited varies greatly. Do you even have any evidence that most supporters of gay marriage are opposed to the legalisation of incestuous marriages (in jurisdictions where they are not already legal)? Or indeed, can you point to any concrete evidence of gay rights advocates campaigning to impose additional restrictions on incestuous relationships?