With that, I have two main problems with the marriage equality movement: 1. That its operation takes a tremendous amount of money, energy, and attention away from far more pressing issues. (Sometimes this is clear and direct, such as California spending $43 million on Prop 8 while $85 million was being cut from HIV/AIDS services. Sometimes this is more subtle, the successes of which can be measured when every single straight person I know uses their approval for same-sex marriage to demonstrate their allyship to me.) 2. That its strategies actively work against movements for queer economic justice, by removing capitalism, meaningful immigration reform, and gender/sexual deviance from the discussion entirely.
It is not a coincidence that the rhetoric, imagery, and marketing of the marriage equality movement is so utterly assimilationist, and this is where my problems extend to issues of personal safety. This movement intentionally and maliciously erases and excludes so many queer people and cultures, particularly trans and gender non-conforming people, poor queer people, and queer people in non-traditional families. This movement whitewashes, breeder-izes, and cis-sexxifies the criteria for acceptance and civil rights, ignoring the most extreme threat to queer and trans people's civil liberties: That if we cannot pass for straight and cissexual, we are deemed worthy of violence, detention, and death. In recent (and predictable) developments, conservatives who have joined the same-sex marriage bandwagon are using it as a wedge against single parents, immigrant families, and others. (Sometimes, the enemy of your new friend... is the person you should actually be friends with.)
Thank you for a well-reasoned response. I am what I would call a straight ally of queer/trans people, and thoroughly support equal rights for all. But I, too, smelled a rat in this latter-day emphasis on same-sex marriage; I kept wondering why liberals were so vocally coming out in favor or what is essentially a conservative (and as you point out, capitalist/property-accumulating) institution. I wondered why the government should even be involved in such definitions, which are more religious and personal than they are legally necessary (and should be covered by laws on cohabitation, common property, and other extensions of legal unions, rather than by "marriage"). I suddenly felt like we were all being taken for a ride.
That's when I raised a similar question in my well populated Facebook ecosystem, and the chorus came in: many stating the same justifications you've stated above, usually in the vein of "Hey, it's one step in the right direction!" Only a few of my friends and followers seemed to understand that our lopsided attention on same-sex marriage might also be distracting us from paying attention to more important, more urgent issues...or worse, that it might even make truly progressive options (such as civil unions, straight or gay; property rights; civil liberties; and a whole host of other issues) even harder to achieve. Few agreed with me, but a handful saw the light (or had already considered similar ideas).
At the same time, the fact that one issue is more important than another does not necessitate that all other activities must be abandoned or ignored until that one is fixed. In a society so well-developed and populated as ours, we have the potential to combat injustice on many fronts. I think, then, that it's important to consider the struggle for same-sex marriage on its own merits, and although you have some legitimate misgivings about the institution (which I will address in a moment), it does act as a banner for progress in civil rights, freedom, democracy, and health, so I'm not sure it can be considered so unimportant that we can't give it our attention now.
At this time, then, I think we have to be prudent enough to realise that the changes we desire will not be achieved in our lifetimes, and we have to instead direct our efforts at laying the groundwork for future generations. On that basis, I see same-sex marriage as a temporary but important compromise. The current construction of the institution is not something that we should revere and grant permanence, but these successes are nonetheless extremely significant steps forward for legal and cultural recognition of equality. Given all this, I think it makes more political and practical sense to first equalise marriage before seeking its dissolution, and there are sure to be many more stages in between before that will eventually come about.
I definitely agree with your sentiment that the fight for marriage equality takes a significant amount of energy away from many more pressing issues facing the LGBT community, and that the majority of people involved in this debate won't put their energy into these issues once marriage has been resolved. However, call me cynical, but I also think that these same people that will be ignoring these same issues wouldn't have fought for them to begin with, regardless of the distraction of the marriage debate. Sadly, I feel like the majority of people (with the obvious exception of true activists) only get involved in causes that they see as directly affecting them. So the stereotypical middle-to-upper class white gay man probably wouldn't be concerned with trans or immigrant rights either way, with or without the involvement in same-sex marriage rights.
Also, how do you respond to the other concrete advantages that come with marriage, such as hospital visitation rights, inheritance rights, and custody rights? Granted, these can all be achieved through civil unions as well, but from what I understand, it is much harder to get these basic rights with a civil union rather than an official marriage. I am sympathetic to the desire for true recognized equality as well, so it seems to me that in order to not support same-sex marriage, one should fight for civil unions for all couples, as opposed to civil unions for gay couples.