This is the heart of the Utopian spirit: Give us tomorrow and we'll make it better--we'll give you a "solution." Therefore, 6000 years of marriage history is called "radical" by people wanting to radically change the definition of marriage.
This adolescent way of looking at the world was something I experienced while working at a video store right after high school. When a customer walked through the doors and turned to me asking: "Is there anything good?" I knew what they meant. They didn't want something "good" they wanted to know if this week's hot new release was in stock. Sometimes for the fun of it I would suggest a great classic film they never could have seen and they just gave me a weird look. By definition, the adolescent mind sees new as good and exciting and old as bad and boring. Try applying liberal policies to this model and you will see what I mean. In the liberal mind, the question is not whether an idea, policy, or law is good or it actually works, but the right question is is it new, exciting, and different.