It’s good for American presidents to meet with adversaries, to clarify differences and resolve disputes. But when President Trump sits down with President Vladimir Putin of Russia in Finland next month, it will be a meeting of kindred spirits, and that’s a problem.

One would think that at a tête-à-tête with the Russian autocrat, the president of the United States would take on some of the major concerns of America and its closest allies. Say, for instance, Mr. Putin’s seizure of Crimea and attack on Ukraine, which led to punishing international sanctions. But at the Group of 7 meeting in Quebec this month, Mr. Trump reportedly told his fellow heads of state that Crimea is Russian because everyone there speaks that language. And, of course, Trump aides talked to Russian officials about lifting some sanctions even before he took office.

One would hope that the president of the United States would let Mr. Putin know that he faces a united front of Mr. Trump and his fellow NATO leaders, with whom he would have met days before the summit in Helsinki. But Axios reported that during the meeting in Quebec, Mr. Trump said, “NATO is as bad as Nafta,” the North American Free Trade Agreement, which is one of Mr. Trump’s favorite boogeymen.

Certainly the president would mention that even the people he appointed to run America’s intelligence services believe unequivocally that Mr. Putin interfered in the 2016 election to put him in office and is continuing to undermine American democracy. Right? But on Thursday morning, Mr. Trump tweeted, “Russia continues to say they had nothing to do with Meddling in our Election!”