That is a touchy-feely answer with no concrete foundation in reality. People have the right to live as they want, the government doesn't have to recognize their choices for them to live their lives.When our citizens have rights and the freedom to live their lives as they choose, society benefits greatly. If we banned Christians (or whatever you identify with) from marrying, would that make America more or less free?
If the government defined marriage as being between two men it wouldn't change my life in the least, but then I don't live my life seeking approval from the government.
It's funny how gay marriage and abortion are really the only facets of modern society where the Left seems at all interested in making a case for "freedom", though. Everywhere else the left is about eliminating freedoms.