The Institution of Marriage and the Traditional Family after Adoption of Same-Sex Marriages

Like any controversial topic, introduction of same-sex marriages has engendered multiple arguments – both in favor and against it – which come from various spheres of social life, from religion to law. For instance, a debatabase website ProCons.org contains 15 arguments for and 13 ones against same-sex marriages ; and one can imagine that the actual number of all possible arguments is by far not limited even to this quantity.
People who have not gone deep into this debate might wonder why this topic is disputable: seemingly, legalization of same-sex marriages is for the benefit of LGBT people, while it does not anyhow harm straight people, therefore, it should leave the latter ones either positive (as satisfaction of other people’s needs somehow brings harmony and friendship to the entire society), or, at least, indifferent (as same-sex marriages are not related to heterosexuals in any way). Speaking in terms of biology, the relationship between gay and straight people on the issue of same-sex marriages can, at the first glance, be viewed as commensalism: one organism turns the relationship to its advantage while the other one is neither better off, nor worse off. Yet, taking a closer look at the debate allows us to understand that both proponents and opponents of gay marriages would strongly disagree with my “commensalism” assumption:
“Amongst the likeliest effects of gay marriage is to take us down a slippery slope to legalized polygamy and ‘polyamory’ (group marriage). Marriage will be transformed into a variety of relationship contracts, linking two, three, or more individuals (however weakly and temporarily) in every conceivable combination of male and female” (Kurtz 2003).

“The announcement I made last week about my views on marriage equality -- same principle. <…> The basic idea -- I want everybody treated fairly in this country. We have never gone wrong when we expanded rights and responsibilities to everybody. That doesn’t weaken families; that strengthens families. It’s the right thing to do” (President Barack Obama, “The View” TV show, 14 May 2012).

Although the two opinions oppose each other, there is one thing they have in common: they both imply that expanding the right to marry to homosexual couples would affect the institutions of family and marriage themselves, either positively or negatively. [...]