I've done some more thinking.
For those who do think it's the government's duty to stop homosexuality [by some means] "cuz its worng," think: why do we choose to have a government to begin with? The government's job is to protect its people. So we ban things--we ban killing, and why? Well, killing leads to death, intruding on the natural rights. We ban stealing for the same reason, reckless driving habits are banned to prevent death, etc.
Tell me, who is being protected from harm when gay people are not allowed to marry each other? No one, really. No one. Therefore the government cannot ban gay marriage, as it's simply not dangerous and violates the personal freedom of nobody.