Of course 9-11 was not "happy". And because we do not want to experience such a "happy" occassion again, we cannot forget what is symbolized.
9-11 symbolized such a radical faith that men and women are willing to die for it. This faith is a faith that is based not on reason, but revelation. It is not just a transcentdental view of life, but also, a political one. Islam is a politicized faith. And such a politicized faith as an absolutist, exclusivistic, and intolerant one, is dangerous indeed. It does not allow women and children basic human rights nor is it open to change. Those who impose laws that support such a faith are intolerant and authoritarian.
Our Founders found a nation based on freedoms. Freedoms from human authorities and based on the "rule of law". Men and women were willing to die for such liberties. Such radical commitment to the values that underwrote our Constitution are what gain human liberty and underwrite human rights movement. America's laws protect individual liberties and are not intolerant, unchanging and authoritarian.
Our nation is known for it opportunites and its innovation. We are a nation that absorbs all cultures and does not discriminate based upon personal convictions. Freedom of thought and speech guaruntees that the public's interest will be won at the ballot box. Our views have been so conditioned by such an environment, that it is hard for us to imagine such an oppressive religious regime. Our Founders protected our society from religious wars by the Establishment Clause.
Now, on the twilight of a decade of struggling against a religious view, our nation finds itself in a type of 'religious war' over legislation and how we should treat those who do not respect the 'rule of law'. This is a dangerous time in our country's history, but not because of "God's impending judgment" upon an ungodly nation, but because of the undermining of our country's valuing of liberty and law. We are unlike any other nation, because we are a government "for the people and by the people". Let us count our blessing todays and not forget the costs of liberty and furthering justice.
Aren't you glad that you live in America?