Perversely, the worse Syria became, the more justified the president seemed for staying aloof; steps that might have helped in 2012 seemed ineffectual by 2013, and actions that could have saved lives in 2013 would not have been up to the challenge presented by 2014. The fact that the woman who wrote the book on genocide, Samantha Power, and the woman who campaigned to bomb Sudan to save the people of Darfur, Susan Rice, could apparently in good conscience stay on as U.N. ambassador and national security adviser, respectively, lent further moral credibility to U.S. abdication.

Most critically, inaction was sold not as a necessary evil but as a notable achievement: The United States at last was leading with the head, not the heart, and with modesty, not arrogance. “Realists” pointed out that the United States gets into trouble when it lets ideals or emotions rule — when it sends soldiers to feed the hungry in Somalia, for example, only to lose them, as told in “ Black Hawk Down,” and turn tail.

The realists were right that the United States has to consider interests as well as values, must pace itself and can’t save everyone. But a values-free argument ought at least to be able to show that the ends have justified the means, whereas the strategic results of Obama’s disengagement have been nearly as disastrous as the human consequences.