ONE OF Vladimir Putin’s fondest conceits is that the U.S. political system is every bit as corrupt, authoritarian and bent on external aggression as his regime. At a meeting with Western academics and ex-statesmen last week in his favorite resort, Sochi, Mr. Putin was at it again: For every crime committed by his Kremlin, Mr. Putin was ready with a comparison to a supposedly identical outrage by the American “ruling class,” as he likes to call it.

The invasions of Crimea and eastern Ukraine? Exactly like NATO’s interventions in Bosnia and Kosovo during the 1990s, says Mr. Putin. The Obama administration’s charge that Russia has attempted to intervene in the U.S. presidential campaign? Mr. Putin responded with the same language used by the White House to answer Moscow’s allegations that Hillary Clinton was behind popular demonstrations against Mr. Putin’s reelection four years ago.

“The majority of citizens,” sighed Mr. Putin, “have no real influence on the political process and no direct and real influence on power.” As for the notion that he supported Donald Trump, Mr. Putin called this orchestrated propaganda of the Clinton camp before observing that Mr. Trump “represents the interests of the sizable part of American society that is tired of the elites that have been in power for decades now . . . and does not like to see power handed down by inheritance.” Maybe that wasn’t an endorsement, but Mr. Putin and Mr. Trump have an uncanny way of echoing each other’s words.

The subject that most seemed to provoke Mr. Putin was Aleppo, where Russian and Syrian bombing of hospitals, apartment buildings and a United Nations relief convoy has been widely condemned as a war crime. “We keep hearing Aleppo, Aleppo, Aleppo,” whined Mr. Putin. Yet the attack on the Syrian city, he contended, was not different from the U.S.-backed assault on Mosul, the Iraqi city held by the Islamic State. “If it is better not to go in” to Aleppo, he contended, “then the offensive against Mosul shouldn’t go ahead either.”

Here, for the record, are some differences: While Mosul is controlled by Islamist extremists who enslave non-Sunni women and behead dissenters, the rebel forces in Aleppo include Western-backed secular groups who seek only to overturn the blood-drenched Assad regime. U.S. and allied planes are not deliberately targeting Mosul’s hospitals or international aid groups. And while the Mosul campaign has broad international support, only Russia, the Assad regime and Iran support the Aleppo attack.

Most people living in open societies are informed enough to perceive the cynicism and mendacity in Mr. Putin’s comparisons. But Russia’s increasingly sophisticated Internet and satellite television propaganda operations are winning over a segment of Western opinion. Mr. Trump, too, has adopted Mr. Putin’s view. He has repeatedly endorsed Moscow’s call for the West to join Russia in fighting “terrorism,” and he has written off Aleppo as “ basically fallen.”

If Mr. Trump is elected, the United States will have a president who sees no essential difference between the U.S. and Russian military offensives in the Middle East. Mr. Putin will be vindicated: The moral gap between his regime and the White House will be difficult to detect.