The argument was that two consenting adults who can marry without harming anybody should be allowed to. A pig is not a consenting adult. As noted above, if a brother and sister procreate, there is a great chance for harm to the child. I'm not convinced that polygamy should be illegal either. Perhaps if it were legal, there would be more control over whether groups like the FDLS would be marrying children and hiding out in compounds. I am of the mind frame that anything that doesn't harm anybody else or infringe on someone else's rights should be legal.
Not allowing gays to be married doesn't change the fact that they are gay and living a gay lifestyle. Allowing gays to be married isn't going to increase the number of homosexuals in our country. Either they are gay or they aren't. Nothing you believe is going to change that fact.
It seems as though our basic difference is that I don't believe you can or should legislate morality and you do. We clearly each feel strongly about that basic premise and we clearly won't be changing each other's minds. I think the debate is worth hashing out and I do appreciate a good debate that is done without insults and name calling