I’m going to keep this short and sweet and just offer a perspective. The motivation for asking is that there has always been, it seems to me, a fair amount of generalized LGBT unease with the notion of ‘traditional marriage’, which is understandable, from a number of perspectives, not the least of which is that almost everyone gay or lesbian had to step out of a ‘tradition’ or ‘identity’ in order to claim their own self and invigorate their own spirituality.
To cut to the chase: The answer, I think, is yes and no.
The “good” news is that, if marriage is “okayed”, almost everyone will probably continue just as they are now, except those who really want the ’ol ball-and-chain can get it, legally. Additional evidence that this is true is that non-gay people can get married, yet today’s society provides a great deal of latitude to be single or to not get married (except if you take on the mega responsibilities of having children, perhaps) or engage in all kinds of sexual activity that might be considered ‘too fun’ by strict standards (I’m thinking of swingers groups for non-gays, etc., that exist quietly within the broader marriage ethic that exists for non-gays, today).
The “bad” news is that the point of having marriage is to express and ethic, and the whole point of an ethic is judge what is perceived to be “right” and “wrong”. No way around it, I don’t think. No such thing as an ethic that everyone can do everything – that’s ultimately self-defeating.
The basic ‘marriage ethic’, as it is now, says that there is a proper context for sexual relations. There are at least two basis for this, the first being the realization that there is a certain spirituality with human sexuality. As the Sufi poet Rumi put it, roughly, when two people make love, they create a child in the ‘spirit world’, which is perhaps to say that there is an emotional responsibility that attaches to acts as profoundly human and natural as having sex, even if the strength of that resonates very differently for individuals. Of course, having a ‘quickie’ is completely possible and ignores this ‘realization’.
But that just brings up the second basis, which is that these ethics have a sort-of ‘collected wisdom’ or a ‘passed on wisdom’ or a ‘shared insight’ character to them. The upshot of this ‘collected wisdom’ is to suggest, via the general understanding of the ethic, that people who have come before have tried a lot of these other things, like ‘quickies’, and they come up empty in the long run as any kind of serious modus vivendi. Put another way, they amount to heuristic beliefs, a short-hand way of saying, “been-there, done-that – better off with something else”. To illustrate further, one element might be the role of fidelity, which is a judgment both about the pitfalls of how high passions run, in general, when one uncovers infidelity and perhaps also a judgment about the shortness of time, that a pattern of repeated break-ups is no more fulfilling than trying to ride out the ups and downs. One element might be the role of family obligations in relation to arranged marriages, which is an important example about how the wisdom in such things is not always enduring because the march of History has a way of changing consciousness and circumstances, circumstances under which arranged marriages “made sense”.
‘Gay marriage’ as an ethic is not going to make other viewpoints go away, viewpoints embodied in phenomenon like ‘Club Hedonism’, an erstwhile resort for non-gays obviously appealing to a different expression. What I would strongly suggest is that it is because there is a dominant, responsible, relationship-oriented ethic, that other things are possible. In other words, it is because the French are married, that they can quietly allow themselves mistresses. In America, Hugh Hefner and his viewpoint are possible, because they take place in a broader context. In fact, when I get around to make the promised ‘liberal case for gay marriage’, it won’t look like the Burkean or Hyakian inflected ‘conservative case’, because it will actually posit the utility to gay people as a group from having a stable, non-threatened, relationship-oriented ethic among non-gay people, even if that means gays accepting the same for themselves. When non-gay relationships start to run off the rails, so to speak, for whatever reason, that is when societies historically have gotten into trouble managing themselves. Sexual minorities, as we all know, such as gays and lesbians, are the first to suffer, when there are social problems amok. (In fact, I would go further to say that the 'one-man, one-woman' ethic, as it is in custom and law now, was the probable result of societies trying to right themselves after periods of topsy-turvy. This view is quite instructive, perhaps, to those like AS, who take Church doctrine, for instance, on the face of it, rather than on the selection of it. Sharing that insight is probably taboo and counter-productive, on a certain calculus, but such things are laid on the table by those opponents whose obstinacy has far-reaching consequences.)
Done right, “gay marriage” will expand freedom for those who want the general relationship protections, rights, and responsibilities of marriage bands (of paramount importance for those who take up the responsibilities of raising children) and it will simply ‘reposition’ those with other viewpoints. Traditionalist and conservatives will continue to rail and warn against the “Playboys” of the world and, in response, “fringe groups” will fight back, gain whatever ‘space’, limit their worst "excesses", but probably not disappear. All that is very familiar and, because it is, suggests society won’t careen toward despair and dissolution. All will be right with the world.