What good moral reason is there for withholding a right to ‘gay marriage’?

I’m afraid John Waters will hate this since his pronouncement that there is no right to a gay marriage is being carried far and wide across the blogosphere, from Manchester to Atlantic uber-blogger Andrew Sullivan… It falls to Norm to dish the dirt on Mr Waters‘ rather imprecise grasp of logic:

Waters might like to consult Article 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.

It reads like the latest instalment of Waters’ crusade for the introduction of the Un-Enlightenment? Norm’s definitive response is:

…the normative content of the right matters more than the meaning of a word, and 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?