Here's desperation for you. In his column in the Irish Times and arguing against a right to gay marriage, John Waters says:
[I]t bears repeating that there is no "human right" to be married... Many people never get married and do not regard themselves as discriminated against.
Waters might like to consult Aricle 16 (1) of the Universal Declaration of Human Rights. It is, of course, true that many people never get married, but this no more shows that there is no human right to marry than the fact of there being large numbers of atheists shows there is no freedom of worship. The right to marry is not a claim right - such that you can insist on someone somewhere being obliged to marry you. But it is a liberty right; it entitles adults to get married if they can find willing partners. Gays are today claiming this right, and to deny its very existence is as feeble a form of opposition to their claim as you'll find.
So, too, is this definitional move (in which, be it noted, some sort of right to marry has reappeared):
Marriage, a contract between a man and a woman, is an institution maintained by society for reasons having little or nothing to do with "love". All men and all women have a right to marry, provided they wish to marry members of the opposite sex to whom they are not closely related by blood. Heterosexuals, like homosexuals, are prohibited from marrying people of their own sex. It is no more valid to allege wrongful discrimination in this context against gays than to argue that cycle lanes "discriminate" wrongfully against wheelbarrows.
The analogy is hopeless. Wheelbarrows, so far as we know, aren't sentient and intelligent beings; they won't feel an injustice. To make the analogy serviceable, let's adapt it as follows: suppose the city declares tomorrow that henceforth all cycle lanes are to be relabelled 'green cycle lanes', and only owners of green bikes may use them. People with blue, black and yellow bikes would have grounds for complaint unless and until the city comes up with a good reason why only the owners of green bikes should be permitted to use the lanes. Better still, imagine there are 'rights of man' and that they determine the liberties and entitlements held to be due to men - but not to women. Then women begin to claim these rights for themselves, calling them human rights, and someone says: 'But they are, by definition, rights exclusively for men'. The answer to this is that the normative content of the right matters more than the meaning of a word, and that the meanings of words evolve. You need a good moral reason to hold the meaning of 'marriage' fixed in the way John Waters wants to. What is that reason?