THE OUTSIDE world seems to have grown numb to reports of atrocities from Syria — “barrel bombs” dropped on schools, Scud missiles aimed at apartment houses, blockaded neighborhoods where children die of starvation. But a report released Monday by a panel of international jurists ought to prick some consciences. Based on 55,000 images smuggled out of the country, mostly by a defector from the military police, it reports the murder of some 11,000 men detained by the Syrian government between 2011 and last August. Many of the bodies in the photographs show signs of torture; some are missing eyes. More than 40 percent of the bodies show signs of emaciation, indicating that the prisoners were systematically starved.

On Wednesday, Secretary of State John F. Kerry opened the Geneva 2 peace conference on Syria by referring to this “horrific” account of “systematic torture and execution of thousands of prisoners.” He called it “an appalling assault, not only on human lives but on human dignity and on every standard by which the international community tries to organize itself.” The jurists, former war-crimes prosecutors commissioned by the government of Qatar, concluded that the “evidence would support findings of crimes against humanity against the current Syrian regime.”

Yet the diplomatic initiative that Mr. Kerry launched offers no means to hold the regime of Bashar al-Assad accountable for these atrocities, or even to stop them. On the contrary: It may serve to prop up the Assad government by treating it as a legitimate party to negotiations about Syria’s future. Mr. Kerry insists the talks will lead to a transitional government that excludes Mr. Assad, but the Syrian delegation flatly rejects this premise, and there is no indication that its allies Russia and Iran think otherwise.

Some diplomats at the conference, such as United Nations mediator Lakhdar Brahimi, believe it could lead to palliative measures, such as local cease-fires and the opening of humanitarian corridors to besieged civilians. Mr. Brahimi’s predecessor, Kofi Annan, was convinced of this as well and even obtained the Assad regime’s formal agreement to a plan. But the Assad forces never respected their commitments; now they are using offers of humanitarian supplies as a means to force the surrender of rebel-held areas.

President Obama demonstrated last year that the credible threat of force could change the regime’s behavior. His promise of airstrikes caused Mr. Assad to surrender an arsenal of chemical weapons . Yet the president seems not to have learned the lesson of that episode. Now he makes the defeatist argument that, as he put it to David Remnick of the New Yorker, “It is very difficult to imagine a scenario in which our involvement in Syria would have led to a better outcome, short of us being willing to undertake an effort in size and scope similar to what we did in Iraq.”

In fact, Mr. Obama probably could force the measures Mr. Brahimi is seeking by presenting Mr. Assad with the choice of accepting them or enduring U.S. airstrikes. That he refuses to consider options between Mr. Kerry’s feckless diplomacy and an Iraq-style invasion only ensures that the Geneva 2 conference will fail and that the atrocities will continue.