Originally posted by Todd K. I am just trying to understand this issue better. Do you support polygamy, gay polygamy, and consensual incestuous marriage, or for that matter consensual incestuous gay marriage? Please explain why or why not.
You are not talking about apples and apples there.
At the civil level, marriage is as much about contractual co-dependence as it is about love. Treatment by the tax code, insurance coverage, immigration, and the court system (testifying against a spouse) all treat married couples differently than they do any other 2 individuals.
Polygamy seriously upsets these policies because it offers so much room for abuse such as sham marriages for immigration, health care, tax avoidance, or protection from prosecution. With polygamy you also have to deal with partial divorce which is a messy enough issue even between two people. Another issue with polygamy is that it creates an imbalance of the sexes because in communities where it has existed in the past there is a problem where the boys are expelled from the society as the reach manhood to reserve the young women for the older men. Those banished young men without prospects for love create a burden on the rest of society, and the retained women are unfairly denied the opportunity to find love amongst their peers.
Incestuous relationships also have a higher potential for some abuse like tax avoidance and insurance fraud, but the main problem with incest is that there is no such thing as a consensual incestuous relationship between two adults because those relationships have been built from childhood.
Besides the civil factors that make it easy for society to handle gay marriage better than the other types of marriage relationships you mention, there is mounting evidence that homosexuality is largely driven by genetics. I have 2 close friends that are gay and I know that it runs in their families. One has 9 brothers and sisters and was raised in a very catholic family (obviously with 10 kids) 5/10 of them are openly gay, 1 of them is a priest, 1 is a nun, and only 3 are married to a member of the opposite sex. She suspects that the priest and the nun are both gay but neither of them admit to it. My other friend is an only child but his mother is the only straight one of four children and her mother was the only one that married out of three children (she thinks her aunts are gay but they came from a generation where it is still to taboo to talk about). In society as a whole I think the prevalence of homosexuality is about 10-20% but in some families it seems to run much higher.