Do you believe all laws are moral?
If not, then what makes a ban on gay marriage moral, and how can you tell? What about abortion? That's a law too.
Should we follow laws that are immoral? (ie. Jim Crow laws).
Rosa Parks broke the law when she sat at the front of the bus. Does that make her an immoral person for breaking the law?
If not, then why is a gay couple breaking the law to get married immoral? Especially since homosexuality and marriage are private matters and do not harm the general public?
If you make the argument that the gay couples in San Francisco are horrible people because they are breaking the law in California, and the law should be abided by, do you ever then think about Rosa Parks who broke the law too?