It's unfortunate that defenders of same-sex marriage often feel compelled to "avoid the slippery slope towards polygamy". It doesn't help that many examples of larger families in the public eye involve patriarchal, traditional Mormon- or Islamic-style polygamy, rather than polyamory where women as well as men are free and empowered partners.
(Polyamorous relationships can be polyfidelitous, as with the Brazilian trio, or open. Not so different from couples.)
Maybe the "old paradigm" thinking of holding up traditional institutions as sacrosanct is starting to give way to the "new paradigm" that instead values the well-being, fulfillment, and happiness of people.
Maybe it's the beginning of non-descrimmination, but having one thing called "marriage" for heterosexual marriages between one man and one woman, and having other terms like "civil unions" or "stable union" and declaring the quasi-religious thing of "marriage is between one man and one woman" to be the only definition of "marriage" is a form of "separate but equal". That didn't work in the early days of racial rights in the midst of segregation, and it won't work now.
I really don't see that the government has any business dictating what a "family" can be, or who can form one, so long as there is freedom of association. If any two or more people wish to declare that they are a "family", have united interests and goals, wish to have their relationship with one another recognized, it shouldn't be anything beyond registration. Of course, it would have to be for adults - people legally able to enter into contracts and be of legal age of consent for sexual activity.
Note that marriage, as defined in the Bible is only between one man and one woman
Customs change over time, and the laws of a nation need to be flexible enough to accommodate such customs.
I am so outraged by the political definition of marriage being surrounded by the biblical definition of marriage. I have a truly great friend who has supported me though a great deal in my lifetime. Heart attack, Breast Cancer, and Hashimoto's Disease. I only look at him as my friend, not my gay friend. I always wish true happiness for him. The Constitution states, "life, liberty, and the pursuit of happiness", not whatever the politician's and lawmaker's say. I really don't think that our forefather's intended us to be so judgmental just because we can.
ORLY? There is an interesting case to be made for homophobia being a European import to many Asian cultures. Homosexual marriages between men (because they were still sexist even if they weren't homophobic) were well-documented in Ming dynasty Fujian, and it was only with the foreign influences of the Qing dynasty that homophobia became the norm.
There have been plenty of cultures throughout history where same-sex partnerships were accepted. I bring up Fujian because it's a unique case in which there actually were legally binding documents to go with the social acceptance of homosexual marriages. (Some African cultures also had socially recognized same-sex marriages, but they weren't much for bureaucracy and record-keeping the way the Chinese were.)
In short, there WERE non-Christian cultures that implemented actual gay marriage. There aren't anymore because the Christians convinced them their ideals were "backwards".
Now, now, the next thing we know, people will be getting marriage licenses for a union of hamsters.