As someone advocating the legalization of first-cousin marriage in all fifty US states, I welcome the discussion of the issue, which is still sorely lacking. And with same-sex marriage receiving far more media coverage, any discussion of cousin marriage is bound to bump up against that debate.
However, I’m disturbed that some of these comparisons have tried to justify legalizing gay marriage by putting down and stigmatizing cousin marriage. This may not be done in most cases, but it sure is unnerving when it is. Plus, these comparisons often reveal a lower level of tolerance for cousin marriage than for gay marriage.
Calling cousin marriage "incest" is an especially nasty put-down that often surfaces in these discussions. It’s an inaccurate insult because incest has a culture-specific definition. In some cultures, it may be considered incest to marry your brother’s widow or someone who happens to share your last name. By calling cousin marriage incest, one is effectively making a value judgment about whether to include it in the definition of incest. And even in regions where cousin marriage unambiguously is considered such and is illegal, it’s a bit like calling gay sex "sodomy." It’s technically true but still very nasty language.
Cousin marriage and gay marriage are not, inviting though the comparison may be, particularly close issues. The numbers of people affected are different: gay marriage affects homosexuals making up perhaps 3% of the population, whereas first- and second-cousin marriages made up around 0.2% of all marriages in studies done fifty years ago. (These are US figures: worldwide the cousin marriage proportion is now over 10%.) Being gay is also at least partly innate, whereas marrying a cousin is a personal choice. Instead, a much better analogy to cousin marriage is surely the anti-miscegenation laws that were last seen in America no later than 1967. In the 1960 census, all interracial couples made up just 0.4% of marriages, while the especially maligned black-white unions made up 0.13%. Interracial marriage is also clearly not innate, like cousin marriage, and is a consciously made choice.
Religiously the issues are enormously different. Gay sex was condemned in the Bible as an "abomination," but sex between cousins such as Jacob and Rachel was not only not condemned but was specifically ordered by God. Even when the Roman Catholic Church later banned cousin marriage, it was understood that this was merely ecclesiastical and not divine law, and consequently the local bishop could and still can dispense from the prohibition. (Such dispensations are much easier to obtain nowadays. They are now almost always granted, effectively allowing first-cousin marriage in Catholicism.) Contrast this to the fervent campaign against gay marriage by socially conservative Catholic officials.
In their social acceptance, how the two issues compare is a curious question. Does anyone have any thoughts on which is more accepted in America today? My guess would be gay marriage, because Americans are shocked by cousin marriage when speaking about the subject abstractly, and I think that most discrimination against married homosexuals would probably be due to their simply being homosexual rather than being married per se.