Interestingly. I saw an article yesterday that was about a pair of siblings, who are in an intimate relationship in the US and want the option of getting married, but it is illegal. They are a half brother and sister who weren't brought up together (share a father, but different mothers). Many of the arguments they were putting forward - "Love is love", "They should have the right to marry whoever they love", "Current laws discriminate against them", "It's no one else's business to judge" etc sounded eerily similar to everything we are hearing in the current SSM debate.
Now, while I find it absurdly ridiculous when we hear those from the 'no' camp (Bernardi and co) relating SSM to people marrying objects, or animals or children (not the slightest relevance, given that you're not talking consenting adult human parties), I find it perplexing that proponents also get so offended by the incestuous or polyamorous relationships being brought up as a Devil's Advocate line of questioning. Nearly like they are so desperate to discredit any points made against, that they are prepared to be hypocritical to the extreme. Not sure how one can argue that anyone should have the right to marry whoever they choose, but then still make exceptions for those that want to marry a close blood relation or more than one person - as I say who are we to judge if all parties are consenting adults? It's not really "Marriage Equality" unless anyone can marry anyone they want.
The only reason I can see is that it is considered taboo (as same sex relationships were considered not so long ago). People often say, because of the chance of genetic defects. However a couple of points here. Apparently the chances of genetic defects, while elevated to the general population, are largely overstated in incestuous breeding. Additionally, are you going to also ban people with inheritable genetic defects to marry and breed? And besides, what's to stop an incestuous couple, worried about the chances of defects, from doing what a lesbian couple does and have children via donor sperm? And what about same sex siblings or half siblings?
The point of all of this? I don't think we can dismiss outright the slippery slope arguments, as dominant narrative does. It's disingenuous to argue that this doesn't open avenues for marriage to evolve further. Now in saying this, I'm not arguing for, or against SSM or indeed, further movement in what constitutes marriage (such as incest). More, it's an interesting point of reference.
