Statements such as these are hypotheticals. So, there will be many opinions. Perhaps something like the Declaration of Independence would have come up later in time? Who knows? If we look at Morrison's statement, he is basically arguing for the importance of the Declaration of Independence. I think from this standpoint, he is correct. The Declaration of Independence (1776) is the most cherished document of our nation and it is the cornerstone of American liberty.
The opening words are almost committed to memory by all citizens and in my opinion, it has made America great. What can be more important than believing that men are created equal, have certain unalienable rights for life, liberty and happiness? Moreover, when the Declaration of Independence says that these points are self-evident, it roots it beyond discussion. It is a fundamental fact of life. These points are essential for a healthy society and many people died to defend these rights.