The mainstream LGBT movement is so strongly wedded to equal rights activism centered around the legal right to gay marriage (often incorrectly and oppressively worded as same sex marriage, and yes, the pun here is intentional; you can groan) that so-called progressive activists both within the supposed LGBT movement (which is really quite often only L and G, and only cis L and G at that) and those who position themselves as allies to it have managed to completely (or conveniently) ignore the oppressiveness of the institution of marriage itself.
1.) Marriage is a classist institution. This I need not explain; it ought to be apparent.
2.) Marriage as defined as a union between two people, regardless of gender or sex, ignores polyamorous relationships of any type. Those of you who have no idea what I'm talking about, I'm not talking about abusive polygamous relationships in which one man has power over several women in a not-really consensual relationship that reeks of misogyny; I'm talking about any kind of polyamorous relationship, regardless of gender distribution, where the folks involved love each other and want to be with each other. And those of you who do know exactly what I mean, I need not explain why marriage and the so-called equal rights campaign repeatedly and consistently denies the validity of your relationships.
Essentially, marriage as advocated completely and utterly invalidates so many forms of relationships that fall outside "relationship between two people." Look no farther than pro-gay marriage signs with messages proclaiming the lesbian or gay holders to be "monogamous" and "committed" to see that one form of oppression is only traded for another, that activism is only a commodity available to those who cannot conceive of oppressions beyond or other than their own -- the hallmark of privilege is not having to ever notice that you have it.
And yes, oppressed people can also be privileged. Ask any Black man or white crip.
3.) Even if every one of the fifty states of the U.S. were to legalize what has come to be termed as "gay marriage," thousands upon thousands of disabled people, queer or straight, will remain unable to wed their partners without severe consequences. In other cases, the presence of legal guardianships or other, less formal but equally impune mechanisms of enforcing power differentials will prevail and coerce disabled people from even being able to make their own decisions about with whom to spend time, let alone whom to love.
4.) Either straight or gay marriage is a binarist and cissexist institution. "Same sex marriage" ignores the basic reality that sex and gender are not the same thing, and either straight or gay marriage ignore the basic reality that not everyone fits into the gender binary to be a man or a woman.
5.) Marriage as legally defined in some jurisdictions serves to enforce compulsory sexuality at the expense of asexuals (or anyone anywhere on the ace spectrum) whenever a condition of marriage involves consummation (aka sex).
6.) Queer folks are disproportionately likely to a. become homeless, b. become suicidal, c. actually commit suicide, d. be victimized by hate crime, e. be multiply marginalized, f. be victimized by police brutality.
And we're concerned about marriage?
What victory is it that only serves to enforce other forms of privilege in the name of throwing off oppression?
7.) Marriage, ultimately, is an institution of privilege that cloaks itself as a human right, when in fact it relies upon legitimizing legal systems and processes that frequently serve only to perpetuate oppressions upon oppressions. And the rhetoric of marriage is one that places value on certain kinds of relationships while asserting, quite aggressively, that relationships that fall outside its model have no place in society.
Marriage is not about love. Marriage is about enforcing dominant, hegemonic ways of performing sexuality and gender within the constraints of an innately oppressive system of law.