The United States has long seen itself as a beacon of democracy and a global advocate of human rights and the rule of law. It has faltered, sometimes badly, undermining leaders whose views did not fit its strategic objectives and replacing them with pliant despots. Yet for the most part American presidents, Republican and Democratic, have believed that the United States should provide a moral compass to the world, encouraging people to pursue their right to self-government and human dignity and rebuking foreign leaders who fall short.

Like so much else under President Trump, though, this idea has now been turned on its head and people are worried about the very survival of the values on which America built its reputation and helped construct an entire international system, including the United Nations. The latest example is Mr. Trump’s decision to invite Rodrigo Duterte, the president of the Philippines, to the White House.

Though the Philippines is an ally and a democracy, Mr. Duterte is neither a democratic leader nor a worthy ally. For about two decades as mayor of Davao, he was accused of allowing death squads to roam the city and kill freely. Most victims were poor drug users and low-level criminals, but bystanders, children and political opponents were also caught up in the bloodshed.

After his election last year, Mr. Duterte took the killing campaign nationwide, effectively giving free license to the police and vigilantes. He has boasted about his tenure in Davao, and admitted to personally killing three kidnappers without trial. The mayhem got so bad that last week a Filipino lawyer formally asked the International Criminal Court to charge Mr. Duterte and 11 officials with mass murder and crimes against humanity over the extrajudicial killings of nearly 10,000 people over the past three decades.