Gay marriage is the main liberatory movement in 2010 -- which goes to show how free everyone is in America, if that's all that's left to fight over. No more slavery, no landowning requirements to vote, no foreign rule, etc.
Freedom-seeking movements will try to get the most liberatory bang for their buck, so they will target sources of oppression that are truly heinous first, then move on to not so oppressive threats, and wind up squabbling over liberation that is so minor that achieving their goal could hardly be taken seriously as a Great Unyoking.
Throughout history, when a horde of invading foreigners took over a community, that community tended to resist, often violently and for long stretches of time. Because the revolt against foreign rule is so widespread across the world, so persistent through time, and so bloody, we infer that the revolutionaries are up against a very oppressive regime.
Gay marriage is at the other end of the spectrum: it appears almost nowhere in the world, even where it does it's only a decade old, and none of the proponents of it are willing to stake their lives for the struggle or even put themselves in front of firehoses. Thus, the denial of marriage rights to homosexuals is scarcely oppressive at all. After all, most gay guys have no plans to ever get married in the first place because, like most straight guys, they'd prefer to cat around until they turn gray. The point about banning gay marriage applies to homophobia in all forms -- fighting it is not widespread, old, or violent, so homophobia cannot have been very oppressive.
In the middle but closer to the anti-imperialist side are anti-slavery movements, including anti-wage slavery movements. They're not quite as widespread, old, and violent, but they're pretty close, especially when they also have an anti-foreign rule angle to them like slave rebellions in the Americas. Slaves and wage slaves are less oppressed than those under the boot of foreign rule because slaveowners at least have some incentive to keep their subjects decently fed, clothed, and housed -- otherwise they won't be able to work and earn the master any money. A foreign ruler is mostly interested in stealing whatever he can, abducting the pretty young women as concubines, and levying crushing taxes on the community that he has no ties to.
In the middle but closer to the gay marriage side is feminism. It's hardly widespread, has only appeared in the past couple centuries, and can get somewhat physically confrontational but rarely at the level of a slave rebellion or an overthrow of a foreign army ruling your land. Why did women the world over and for almost all of time feel that they weren't being oppressed? Well, they surely did see many restrictions on their freedom -- who they could date or marry, whether or not they could own property, etc. -- but they saw that men faced just as severe of restrictions on their freedom, albeit in different domains of life.
When a neighboring tribe or army comes through the village, guess who has no choice but to go face them in defense of their community? When someone needs to labor away at tracking down and hunting game animals to provide the animal fat and protein that we rely on, guess who gets conscripted into the hunting party? When a fight breaks out among the locals, guess who has to step in to break it up before it spills over? Men have brought home the bacon (not merely nuts and berries) and have protected women from violence and other threats to their safety, and they have no real choice to shirk these duties if they want to make it in the world. Women judged the drudgery of the woman's role as no more oppressive than the unavoidable danger of the man's role, so they didn't see any point in fighting for greater personal freedoms.
Only when most threats to a woman's physical safety were eliminated, and after the economy allowed them to bring home the bacon (from the supermarket with wages they earned), did they see an imbalance in how nice overall the guys and the girls had it. And even then most women weren't dyed-in-the-wool bra-burners, so this recent imbalance must not have been very oppressive either, contrary to all of those "prisoner of suburban domesticity" narratives about the 1950s.
The typical civil libertarian sees the world in black and white -- some group is being oppressed or not, and they don't focus much on the magnitude of oppression. Minor infractions must be fought on principle. In the real world, activists should target causes that will deliver the most freedom for the least effort, and go down the list of oppressed groups in order. The fact that so many spend such a large chunk of their outrage budget on trivial matters like gay marriage proves that they do not have liberatory goals, but must be more interested in other things like signaling the purity of their worldview to those whose approval they seek. Like I said, there's not much to fight over these days, but surely something greater than gay marriage -- ending the form of state-sanctioned discrimination known as affirmative action, for example.