Editor's note: John P. Avlon is a CNN contributor and senior political columnist for The Daily Beast. He is the author of "Wingnuts: How the Lunatic Fringe Is Hijacking America."
(CNN) -- The ninth anniversary of 9/11 finds our country divided.
"The warm courage of national unity"-- that was the FDR quote invoked by President George W. Bush at a prayer service in the fall of 2001. It captured the spirit infusing America at the time.
Now, nine years later, our country is fractured into factions on the right and left, even on the solemn subject of the deadliest terrorist attack in American history.
The memory of September 11th is becoming a partisan political football and a focus of increasing anger against American Muslims. (Both impulses were consciously and consistently condemned in the days after 9/11.)
No less objectionable, 9/11 amnesia has taken hold for some. They suggest that America might have overreacted in the aftermath. After all, they say, there was no subsequent successful attack.
Calls for withdrawal from Afghanistan have increased. And I have noticed an uncomfortable sense of obligation in the remembrances this year, a desire to turn the page. For the first time, unrelated events are scheduled without apology or mention of the deeper significance of the date.
I understand, of course, the passage of time. We assimilate the facts of loss into our lives and we move on. Those of us who witnessed the attacks up close keep the scars longer than most.
But when we pledged to honor the sacrifice of those who died so that others might live, that was not an idle promise. We have to mean it. We have to keep faith.
One of the best ways to keep do that is to remember what seemed so clear that painful day -- that we are all Americans and that what unites us is far greater than those things that divide us.
The destruction of the World Trade Center was not a "tragedy" -- we should strike that word from all memorials and remembrances. It was an attack, a conscious act of war.
The evil men who perverted one of the world's primary religions to justify mass murder did not dream of distinguishing between Democrats or Republicans that day -- just as their inheritors today still want to indiscriminately kill as many Americans as possible, no matter whether our president is named George Walker Bush or Barack Hussein Obama.
This is a non-optional conflict.
It is a not a war between America and Islam -- as President Bush and Mayor Rudy Giuliani made repeatedly clear hours after the attacks. Instead, it is a war between centuries, a question of civilization versus barbarism.
And when you're fighting a monster, it's best not to become a monster. Otherwise, the idiots who claim moral equivalence gain a foothold in someone's mind.
Yes, it's surreal that nine years after 9/11, we're debating whether a mosque and Islamic center should be built two blocks from ground zero. That the debate is happening at all is itself a symbol of our tolerance and pluralism -- an example of what separates us from the terrorists.
It is no less surreal that Osama bin Laden is still at large while a hole still gapes in the ground where the World Trade Center once stood. It is no less surreal that an overtly political anti-mosque rally at ground zero is being hosted by advocates peddling a book called "The Post-American Presidency: The Obama Administration's War on America."
It is no less surreal that a church in Florida is marking the ninth anniversary with a "Burn a Quran" Day, despite the warnings by Gen. David Petraeus that such a display of ignorance makes things more difficult and dangerous for our troops on the ground in Afghanistan.
We should remember September 11th as a time of trial and unity. We don't have the luxury of dividing ourselves into "us" against "them" here at home. We're already facing an enemy that does that indiscriminately.
This war is real and ongoing, and not just in the mountains of Afghanistan fighting the Taliban.
We have faced nearly 20 unsuccessful terrorist attacks (at least that we know of) at home since 9/11. And to ultimately win this war, we need to form the broadest possible coalition against radical Islamist terrorists, including and especially acculturated American Muslims who can create an irrefutable counterexample within the Muslim world.
We cannot afford to wait for another attack to unite us as a nation.
Partisan politics have no place on the anniversary of 9/11. We should be mindful of the Cold War wisdom that said partisan politics ought to end at the water's edge. Any reflection of the group hatred that inspired the attacks should not be incubated or tolerated inside the United States.
America is great because we are good. We still possess the unparalleled strength that comes from a diverse people choosing to live in freedom. And we honor our dead by extending the example they set that dark day by meeting the worst of humanity with the best of humanity.
The opinions expressed in this commentary are solely those of John Avlon.