Far too many people speak of "rights" as if they were somehow inherent in the nature of reality and irrefutable, even as if they had some physical existence, when they are nothing of the sort. Rights are what we, as a society, grant to ourselves and agree to mutually respect and support, they are not some inflexible universal law, and that's why they're so terribly difficult to preserve.
A bill of rights is just an inert piece of paper; it serves only as a reminder to society of the rules it agreed it would abide by - the only force to protect those rights is the conscious decision of the people, and they could just as easily decide not to honour that agreement. The current mechanism that ensures people usually do decide to enforce what are generally held to be human rights is, in fact, disturbingly irrational, almost religious. People talk of "rights" and "universal truths" in much the same way as they talk of gods, as if they had an existence of their own outside the human mind and, just like a theist can persuade himself in the face of commandments like "thou shalt not kill", that genocide on this particular occasion would in fact please his god, they can often convince themselves of the validity of a total distortion or even reversal of human rights if the pressure to do so is sufficiently high. Needless to say, this worries me, in the same way that the continued prevalence of cults and superstitions does, and just as rationalism has provided us with a far more accurate and useful scientific worldview than religious fairytales have, we need rational, logical and thus irrefutable reasons to convince one another to preserve each others' rights, not merely a comparatively ignorant assumption that they are the way things should be or a strong yet vague and often brittle reverence for them caused by mere cultural conditioning.
So, in regard to the original post - there's absolutely no reason to instinctively suppose that whatever rights are afforded to homosexuals today are inherently moral and correct, and that no improvement can be made to them. I shall endeavour to work to a logical conclusion, but all logic regrettably requires axioms to start with. I shall start with the axioms of consistency and the reduction of net human suffering as actively or deliberately imposed by others - I think these are fundamental enough that we can all agree on them, but I suspect they could be reduced to corollaries of other, even more fundamental axioms if we were to expand the discussion to a larger aspect of humanity and the universe as a whole; if you don't use the same axioms then further debate is futile and consensus impossible. We will start with consistency, which is fundamental to rationalism itself, and here simply requires that everyone receive equal treatment. You, as (I presume) a heterosexual, have the right to marry someone of the opposite gender, and so does a homosexual. Unlike a homosexual, however, you have the right to marry someone you can love and feel sexual attraction towards, and a homosexual currently does not. Is there any possible reason for you to uphold this inconsistent situation, other than random and unsupportable dictates from whatever god you believe in?
The only answer you could give even worth considering would be to appeal to my other axiom of reducing deliberate causation of suffering, and claim, as many already laughably do, the emotional trauma you, as (I assume) a homophobe, would feel at the knowledge that gays were getting married, due to your disgust and/or bizarre perception that it somehow damages your own marriage. But, unlike the comparable emotional trauma you currently, actively cause to homosexuals by opposing their marriage to one of the same gender, I think we can safely assume that most of them aren't deliberately getting married just to hurt and upset you.
