Please source this. I have read his dedication speech and saw nothing of the sort and the only other objects that he refused were an atom, requested by an atheist group and the MLK Jr "I Have a Dream" speech according to the court opinion. The court also acknowledged that the rotunda was not a public forum in which any group could place objects of their choosing.
It wasn't in the dedication speech. It was in remarks to the press after the brou-ha-ha started. Please see below.
Meanwhile, in America, when asked on CNN whether principles of religious equality would lead him to support an Islamic monument similar to the two-ton commandments, Moore replied, "This nation was founded upon the laws of God, not upon the Koran." In the Christian press, Moore went even further: "This country wasn't founded upon Allah; it was founded upon the Holy Bible, and the question is whether we [Christians] are going to take a stand."
http://www.tompaine.com/feature2.cfm/ID/8728
Asked on CNN whether he would support an Islamic monument to the Koran in the rotunda of the federal building, Moore replied, "This nation was founded upon the laws of God, not upon the Koran. That's clear in the Declaration [of Independence], so it wouldn't fit history and it wouldn't fit law." http://www.cnn.com/2003/LAW/08/22/ten.commandments/index.html