This article makes an excellent point about Dr. Martin Luther King... he was a dreamer, yes, but sadly those are about the only words of his that most people remember. He also spoke truthfully about the nightmare that most African-Americans faced then, and the author details the difficulties that still exist for so many. Dr. King's vision is not yet fulfilled.
This is true of the vision of America's fouding fathers. They voiced some of the most stirring words about the future of humankind, yet their vision has yet to be wholly fulfilled as well. Nor would they recognize how we strive to fulfill the vision of equality for all... they would have been quite startled at giving equal rights to all classes, to women, to African-Americans, to LGBT people. Yet what they articulated remains our goal.