Dubya is a politician and he was trying to be politically correct.
Not all folks under the heading of "Christian" are members of the KKK, the Spanish Inquisition, the Crusades, or the militia folk who hate the U.S. government. And not all Muslims are bombing and mutilating women and children. I think President Bush was trying to emphasize that.
In this country, we have "freedom of religion." There are Americans who are Muslim, Jewish, JW's, Mormons, Christians, Buddhists, etc. They have that right and our government should not promote any of those religious systems nor should it try to prohibit folks from practicing those religions as long as they do not conflict with established civil laws.
The way I understand
John 14:6,
Acts 4:12, and
1 Tim 2:5, Jesus, the Apostle Peter, and the Apostle Paul all declared that the only way to God is through Jesus. Many believe this is true but we cannot try to force others to believe that, neither can we slander and put down those who believe otherwise.