Should same-sex marriage be legal?

By marriage we mean the legal union, not the religious ceremony. For the purposes of this debate, we take gender and sex to be the same concepts.

Pro

 * Forbidding a gay or lesbian couple from marriage when it's explicitly available to a heterosexual couple is preventing their freedom of expression, which is a human right.
 * There are many ways to live a healthy sexuality outside of marriage, such as free union for example.
 * This does not object to the original argument. Heterosexual people may also engage in a free union as well. This objection would fall under a critique against the institution of marriage as a whole and not same-sex marriage.
 * Freedom of expression and freedom of contract are quite distinct things. If one understands expression to mean anything one does in that one thereby expresses oneself, then the notion of freedom of expression becomes the same as the notion of freedom, and that cannot be the intention of the term. In the first approximation, freedom of expression is the freedom of speech, and entering into a contract is not speech.
 * Entering into a contract seems to be speech: one says one agrees to something said and declares that to be binding.
 * Interesting. That would mean that freedom of speech would include freedom of contract. Thus, the freedom to sell oneself into slavery would be protected by freedom of speech. That is almost certainly not meant by freedom of speech, regardless of the definition of the term and its loopholes. Freedom of speech involves right to express ideas, opinions, and impart information, not to enter into agreement.
 * That would mean making imperative statements would not be protected speech.
 * Perhaps it is, perhaps it is not. The essence of freedom of speech is not protection of imperatives. In fact, imperatives can be rephrased as recommendations or statements of what is good: thus, instead of saying "Do X", one may say "it would be good for you to do X". Thus, even if there was prohibition on imperatives, expressing one's ideas about what is good for someone would allow most of what one needs to achieve by imperatives anyway.
 * That would be cheating.
 * It would. Is not non-literal speech great? Cheating is one of the multiple main purposes of non-literal speech.
 * Forbidding gay marriage is making their union less valuable than another's by preventing it from reaching an official level.
 * Marriage is no longer based on complementary, gender-based roles, and therefore the gender of participants no longer matters.
 * It could be argued that marriage itself simply no longer matters, therefore rendering same-sex marriage unnecessary.
 * So you are saying marriage is not necessary for same-sex couples. If so why would it be necessary for opposite-sex cupules. You are saying that any marriage should be illegal?
 * The argument doesn't advocate the illegality of marriage. It claims that marriage has been rendered redundant because its defining essence - the complementing of gendered opposites based on what they are expected to provide in partnership - is redundant, exhibiting a shift in values from the past when marriage was supposedly introduced for this purpose. If the purpose for marriage is nebulous, so are its criteria, including the sexes involved.
 * There will always be roles, even in same-sex couples there are roles.
 * This should be a comment and not an objection. Otherwise, the implication would be that same-sex marriage  should not be legalized as the marriage is based on gender roles.
 * Yes, but the roles would not be legally based on the gender of the partners (e.g. in most modern societies, a woman can work and her man stays at home, in a same sex marriage, one of the 2 might also work while the other stays at home).

Con

 * Marriage has been understood as the union or legal contract between a man and a woman for millennia. If homosexual people want equal rights, they may have them, but there is no need to force the meaning of such a long-lasting and traditional institution as marriage.
 * Marriage recognition can be classed as an equal right in itself.
 * This supposed "right" might infringe on the right of, say, a baker who's a Christian fundamentalist not to make cakes for same-sex newlyweds.
 * Social concepts change, usually not because they are 'forced' or because they are attacks on the traditional, but simply because society evolves. Traditions are abandoned, changed, or conserved throughout history. For example, homosexual marriage is no more than non-Christians marrying are an attack on Christian marriage.
 * The Bible doesn't forbid heathens from marrying, and it probably frowns on Christian men from taking the heathen wives of heathen men as their own (probably arguing that such would constitute adultery): it does, however, forbid homosexuality (at least w:MSM), and thus implicitly at least, gay marriage.
 * The Biblical proscription on MHSWM might nonetheless allow for women to marry women (as WHSWW isn't forbidden in the Old Testament, and in the New Testament the proscription is either vague or describes women lusting for women as a curse by God against selfish women (and thus not a sin—much like painful labors was/is a curse placed by God on women because Eve ate to Forbidden Fruit and beguiled Adam to do the same, but painful labor itself is not necessarily a sin). Also gay marriages can be platonic.
 * The objection here seems to be the use of the term "marriage". If we called it "garriage" would that help? In the end if it walks like a duck, quacks like a duck and swims like a duck then call it a duck (Duck test). How does a gay marriage devalue or affect in anyway a hetero marriage when they are totally de-coupled event?
 * It is not clear at all in this argument why is it that homosexual marriage ´forces´ the institution of heterosexual marriage.
 * It could be used against bakers who don't want to make cakes for gay newlyweds.
 * "Marriage has been understood as the union or legal contract between a man and a woman for millennia", because for millennia society has been homophobic. The fact that something has been done the same for a long time is not a valid argument, because people can be wrong for millennia.
 * "Marriage has been understood as the union or legal contract between a man and a woman for millennia": and by that we mean for a few 1000s years in some notable societies (Ancient Rome, Ancient Egypt, Ancient India, Ancient China); e.g. we know very little about the Etruscan language much less about their marriages. Unless one subscribes to w:YEC, humans have been around for 10 0000s of, arguably over 100 000, years. Those who use this argument of how we lived millennia ago might want to read History of same-sex unions
 * We're referring to civilized people, not a bunch of savage cavemen.
 * Arguments over rights shouldn't be based on assumptions about our early ancestors that are probably incorrect. Further, we moderns are arguably better than the ancients (e.g. Jesus might have healed lepers and the blind in perhaps heartless societies, but in a few liberal European countries, such are well cared for).

No marriage should be recognized

 * Aside from things such as civic unions, government should get out of the marriage business. Let individuals, or perhaps also their communities, internally validate the quality of their personal relationships. There are people who are married who might as well not be; and there are people who are married in all but designation.
 * The state should not interfere in people's personal relationships.