Editor's note: Amjad Atallah is the director of the Middle East Task Force at the New America Foundation and an editor for the Middle East Channel at ForeignPolicy.com.
(CNN) -- President Obama, in his memorable speech almost exactly one year ago in Cairo, Egypt, urged Palestinians to pursue nonviolent means toward securing their freedom and raised the hopes of many Muslim-majority nations who saw a new, unbiased Mideast policy in the making. Those hopes were shattered by America's tepid response to the killings aboard a ship on a peaceful humanitarian mission Sunday night.
A year ago in June, Obama told the Muslim world: "Palestinians must abandon violence. Resistance through violence and killing is wrong and does not succeed." Like the civil rights movement in the United States, "this same story can be told by people from South Africa to South Asia; from Eastern Europe to Indonesia. It's a story with a simple truth: that violence is a dead end.
"It is a sign of neither courage nor power to shoot rockets at sleeping children, or to blow up old women on a bus. That is not how moral authority is claimed; that is how it is surrendered. [....]
"Israel must also live up to its obligations to ensure that Palestinians can live, and work, and develop their society. And just as it devastates Palestinian families, the continuing humanitarian crisis in Gaza does not serve Israel's security; neither does the continuing lack of opportunity in the West Bank."
Consider those words in light of what happened in international waters off the coast of Gaza this weekend. Six ships from Turkey, Greece and Sweden carrying humanitarian supplies -- the same humanitarian supplies the United States government has unsuccessfully insisted Israel allow into Gaza for more than a year now -- were boarded by Israeli commandos.
More than 600 human rights activists, including a Nobel Prize laureate, European and Turkish politicians and activists, and Turkish and Al-Jazeera journalists were accompanying 10 tons of humanitarian aid.
The killings all reportedly happened on the main aid ship, the Mavi Marmara. Israeli news accounts suggest that at least nine and as many as 16 of the civilians on the ship were killed by Israeli commandos. The Israeli government says the killings were in self-defense.
International response has been swift. Turkey, the European Union, Britain, France, Spain, Greece, Ireland, Russia, the United Nations secretary-general and others have all denounced the Israeli attack and called for a lifting of the siege on Gaza. Almost no Israeli ally has been willing to provide Israel with cover for its actions.
By stark contrast with all the leading members of the international community, the United States has responded with a mild statement noting that "the United States deeply regrets the loss of life and injuries sustained, and is currently working to understand the circumstances surrounding this tragedy."
But, in fact, the United States has helped promote the circumstances surrounding this crime by simultaneously urging nonviolent resistance to Israel's occupation, while defending Israeli violence against those who follow that path.
On the one hand, the United States has clearly sided with the international community for more than a year now, demanding that the siege be lifted in Gaza and that Palestinians and their supporters try to emulate the civil rights struggle in the United States and the struggle against apartheid in South Africa.
The Freedom Flotilla, which was attacked this weekend; the ongoing nonviolent demonstrations against the Israeli wall and fence on Palestinian territory; and the boycotts of settler products and companies that operate on occupied Palestinian territory are all efforts that began before Obama's call, but have received increased impetus as a result of his eloquent speech in Cairo last year.
By contrast, the United States has no strategy to encourage Israel to stop the siege or to refrain from assaulting nonviolent civilian activists, which means the Israeli government has felt no compunction to do so.
In the same 24-hour period that Israeli commandos killed civilians on the ship, an American woman -- Emily Henochowicz, a student at New York's Cooper Union -- demonstrating with Palestinians and other internationals near Ramallah, West Bank, was shot in the face with a tear gas canister, reportedly by Israeli soldiers, and lost an eye.
Israel is fully confident that it can continue escalating violence against the nonviolent protests with the United States as an indulgent, if embarrassed, parent watching on.
Israel may be right that it can ignore every nation in the world as long as the United States supports its actions, even when they contradict the president's own demands. This has led Israel into a downward spiral of action against human rights activists that has left even its own supporters and citizens concerned.
The consequences for U.S. policy in the Middle East, and perhaps even for American troops in Iraq and Afghanistan, could be dire. Already there have been demonstrations in Iraq.
Having just returned from an international conference in Qatar, I was struck by the level of disappointment in the United States and the waning hope that Obama might be able to turn his Cairo speech into U.S. policy -- and this was before America's unwillingness to join the rest of the world in denouncing this weekend's killings -- or even the injuring of American citizens such as Henochowicz.
U.S. and Israeli national interests, as defined by our respective governments, now obviously diverge. Pretending otherwise means that, in practice, the United States will subjugate its own interests to those of the right-wing coalition in Israel. You can be sure that Muslims, Europeans, Arabs and human rights activists throughout the world will be paying attention -- both allies and rivals alike.
The opinions expressed in this commentary are solely those of Amjad Atallah.