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 opp

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?