This isn't an easy one, as I get frustrated very quickly with folks that employ emotion as a substitute for logic and rational thought. That said, I'll try and puncture a few myths and restrain my, umm, negativity.
Gay marriage is a good thing, and not just for the gay folks.
Marriage has a lot of little societal side benefits, no least of which involve geriatric end-term, health care generally, and epidemiology specifically. Put simply - sick folks, old folks, and terminally ill folks cost money.
To steal from Bruce Bawer, in (if I recall correctly) his volume "Beyond Queer", it's been pointed out that folks that are in committed relationships tend to live longer, healthier, and more self-sufficient lives. I.e., they cost us all less money, and this is true regardless of their orientation.
Finally, counterintuitive as it may be, divorce is a *grand* thing compared to "make it up as you go along", as are established inheritance, visitation, child custody, and mutual support structures. Throw in the fact that more and more LGBT couples are having or adopting kids together, and encouraging long term relationships begins include that hoary old "for the children" ring.
I will be the first to admit that a fair amount of catting around goes on in the LGBT community, and if anything, that catting around is more endemic to the LGBT community than the mainstream community. I further suggest that this leads to the spread of infection at elevated rates, depression, and a lack of stable sustaining relationships providing the partnership of a spouse as old age approaches.
It is my (less than original) suggestion that opening an institution of the mainstream community, marriage, to LGBT folks is a step in the right direction. Frankly, I would be happy if LGBT marriage bumped up the ratio of successful long term relationships by even 10% - but getting to the 50% failure rate of heterosexual marriage would simply thrill me.
To the extent that committed relationships involve partners that aren't out fooling around on a random basis, regardless of their serological status, they are no longer out in the biological pool. If they are positive with one thing or another, they aren't out there sharing on a broad basis, and if they are negative, they have enhanced chances of staying in that status. Win-win. In societal terms, folks turning up positive for major infectious disease is a huge cost, and prevention saves big, and when such measures are *voluntary* the savings are both bigger (no enforcement cost), and respect civil rights at the same time.
One of the saving graces of marriage is that folks engaged upon it seem to stay independent later in life - good both at the level of individual happiness, and at the grimly fiscal level where as folks go into long term care settings, public expense of maintaining them kicks in at seriously significant levels. That folks should remain independent, and happier, and do so at less expense to the taxpayer seems desirable.
For the children of LGBT unions, promoting stability in those unions (and an organized structure for custody in case of dissolution of those unions) also seems rather a good notion. Presently, judicial response ranges from refusing to hear cases at all as being "outside the law", transferring sole custody to the biological parent (who may or may not be someone the child has ever *met*), to treating the case as judicially equivalent to the child of any other unmarried couple...with responses not even consistent within a given state or appellate system.
Divorce is a grand thing, especially when you don't have it as an option. If a dissolution goes well, then it's not terribly significant - but if there are disputes regarding property, child or pet custody (emotionally a lot of folks go to the same place on these two), or support things can get hairy in a hurry. Having a nice impartial third party to lay it out in front of (a judge) if it all hits the fan, and some sort of structure available is just a lovely thing.
Visitation - it's not *nice* when ones life partner is in the hospital and the estranged relatives turn up and bar you from the facility, when the facility refuses to recognizes signed mutual powers of attorney, etc ad nauseum.
Two partners in Tacoma lived a long and happy life together - one partner ran the business, the other (by mutual agreement) was in charge of home & social arrangements. The business owning partner passed away - and the courts of WA in the face of hostile family claims ended up giving all products of the relationship to the family of the deceased partner, impoverishing a man in his late 60's and throwing him out of the home he'd shared with his partner for decades. Not nice. To some, inheritance seems an issue of greed - but far more often, just as in heterosexual relationships, it is a matter of long term planning and mutual survival in the face of age, retirement, and geriatric care.
The list goes on (there are hundreds of benefits concomitant to marriage vs. unrecognized relationships), but the above rather hits the high points that leap to mind pre-coffee.
Gay marriage is a scary thing only to the easily misled, and a delightfully useful tool for those who would manipulate them.
Gay marriage doesn't threaten any other form of marriage. Both in Massachusetts and abroad, we have not seen huge numbers of heterosexuals screaming in terror and rushing out to obtain divorces or refusing to marry in the presence of lawfully recognized same sex marriage.
Rather, what we've seen is the use of the same sex marriage issue as a red flag to wave in front of the easily provoked as a handy tool for those who prefer emotional manipulation to logical argument as a mechanism to achieve their political ends.
It's always easier to demonize a designated "goat" as a distraction than it is to justify questionable policy. Start a war, dangle some fresh bait, throw a few red herring - and while the feeding frenzy progresses, accomplish a few things you couldn't in the light of day.
For myself...my observation is that relationship dynamics seem to become more complex in geometric progression for each person you add to said relationship, and I figure I'm doing well if I can find one partner with whom I can settle without complicating things with additional players; on the other hand, as long as everyone involved is a consenting adult and I'm not required to play, I don't see what business it is of mine how they arrange their personal lives - what matters to me is creating incentives that whatever funky structure they build amongst themselves should be long term, and further, have a planned end game in case of failure.
Now...that's not terribly romantic, and it's not terribly orthodox..but it is goal-oriented. My suggestion is that functional long term relationships are what we want, as a society, to promote...and that failing that, domestic drama is desirable to minimize and a planned end game (divorce) accomplishes that secondary goal.Granted, I'm not the most eloquent on this or most other topics, but that's the best I can do on a Monday morning...:)