[foldr]

Are you kidding around at this point? On average, people who are married are going to have sex with a smaller number of distinct partners than people who aren’t married. Gay marriage, if it has a significant effect on gay sexual behavior at all, will clearly reduce the risk of HIV transmission.

With regard to sibling marriage, the issue isn't sex per se but children. Although I am not myself deeply opposed to sibling marriage, there are many couples who strongly prefer not to have children outside of marriage, so it is quite reasonable to assume that banning sibling marriage will reduce the number of children of siblings. In contrast, it would simply be laughable to suggest that any significant fraction of gay people who have unprotected sex reserve unprotected sex for marriage. If that were so, HIV would not be a problem in the gay community!

So, no, there is obviously no reasonable comparison between your two cases, as a few moments of thought would make clear.

[ikeboy]

>On average, people who are married are going to have sex with a smaller number of distinct partners than people who aren’t married. Thus, gay marriage, if it has a significant effect on gay sexual behavior at all, will clearly reduce the risk of HIV transmission.

You're neglecting the possibility of increased gay sex due to wider acceptance, which would affect even unmarried gays.

Can you make the argument for higher risk from legalizing incest in your own words, so we can see why it wouldn't apply here?

[foldr]

I'm neglecting it because it's not a realistic possibility. You can't just imagine any old wacky scenario and use it as the basis of your argument -- it has to be plausible.

Gay marriage would most likely have no significant effect on male-to-male HIV transmission rates. In contrast, it is quite obvious that legalizing sibling marriages could encourage siblings to have children, thus increasing the risk of babies born with genetic defects. That being said, it is not clear to me that this constitutes sufficient grounds for making sibling marriage illegal, and I am not strongly opposed to legalizing it.

If you seriously think that there are lots of gay men out there just waiting for gay marriage to be legalized so that they can have lots of unprotected sex, then you really need to increase the diversity of your social circle.

[ikeboy]

>Gay marriage would most likely have no significant effect on male-to-male HIV transmission rates. In contrast, it is quite obvious that legalizing sibling marriages could encourage siblings to have children, thus increasing the risk of babies born with genetic defects.

Is there any difference between the two that's relevant legally? And do you have any more robust defense for the distinction? Your argument above made some sense when distinguishing overall gay sex increasing from risk increasing, but you seem to have abandoned that in your last sentence.

>If you seriously think that there are lots of gay men out there just waiting for gay marriage to be legalized so that they can have lots of unprotected sex, then you really need to increase the diversity of your social circle.

I could say the same about sibling marriage for you. "If you seriously think that there are lots of siblings out there just waiting for sibling marriage to be legalized so that they can have lots of unprotected sex, then you really need to increase the diversity of your social circle."

I wasn't expressing any opinions on what any particular law would lead to, just that the reasoning being used was inconsistent.

>You can't just imagine any old wacky scenario and use it as the basis of your argument -- it has to be plausible.

But this exact scenario is the basis of the argument above against sibling sex.

[foldr]

>Is there any difference between the two that's relevant legally

Yes, the difference between how gay marriage would affect the risk of HIV transmission vs. how sibling marriage would affect the incidence of genetic defects in babies.

>Your argument above made some sense when distinguishing overall gay sex increasing from risk increasing, but you seem to have abandoned that in your last sentence

I'm not sure what you mean. Gay marriage will neither increase the total amount of gay sex nor increase the risk of HIV transmission. There is simply no connection between HIV and gay marriage, so it would make no sense to try to use HIV to justify a ban on gay marriage.

>I could say the same about sibling marriage for you

You could, except that it wouldn't be true. Having children outside of marriage is still a big deal for a significant number of people. Unprotected casual sex is, virtually by definition, not something that appeals primarily to people who want to get married. Again, the facts are important. You can't just make up crazy hypothetical scenarios and use them as the basis of your argument.