Russian flags fly over Moskovsky Prospect in St. Petersburg, Russia, April 4.

Photo: anatoly maltsev/Shutterstock

I served in the Trump administration and fiercely defended the former president. During his administration, no dictator dared do anything close to what Vladimir Putin is doing in Ukraine now. But the things some America-first conservatives are now saying about Mr. Putin alarm me.

I noticed this after I condemned Russia’s invasion in a group chat with Trump appointees. One replied with a Z, the pro-Russia war symbol. One made a vulgar suggestion that President Volodymyr Zelensky was crooked. Others supported Ukraine, and it was clear our group was splitting into two factions.

That split within the right has emerged publicly as well. “Putin has laid out what he wants in Ukraine—a decent starting point,” congressional candidate Joe Kent said March 31, speaking at what was styled an “emergency” conference called “Up From Chaos.” Mr. Kent, who is challenging Rep. Jaime Herrera Beutler (R., Wash.) in a primary, called Mr. Putin’s demand that Ukraine cede Donetsk and Luhansk “very reasonable.” Helen Andrews, a senior editor for American Conservative magazine said, “Ukraine is a corrupt country. Come and get me.”

Also on March 31, Compact magazine released a declaration, signed by 33 people on both the right and left, including former Trump White House aide Michael Anton and journalist Glenn Greenwald. It calls for “de-escalation” and “good-faith” peace talks that acknowledge Russia’s “legitimate security needs” and demands that President Biden disavow “regime change” in Moscow.

Other America-firsters have made comments that sound like Russian propaganda. Rep. Marjorie Taylor Greene (R., Ga.) tweeted that U.S. tax dollars shouldn’t be spent on “lethal aid to be given to possible Nazi militias that are torturing innocent people, especially young children and women.” Charlie Kirk, president of Turning Point USA, tweeted that “if you are mindlessly supporting Ukraine . . . you might be cheering for literal Nazis.”

Some of these arguments are made in earnest; others perhaps are mere efforts to be edgy. One might think they’re harmless, but they potentially influence millions of American conservatives, and Russian state media has republished some of them to push the lie that Ukraine is overrun by Nazis targeting Russian civilians. They also damage the credibility of the America-first movement.

Some of my former colleagues buy into Mr. Putin’s false narratives because they mistake him for a Russian Donald Trump—a strong nationalist leader who fights woke ideas. But the war against Ukraine hasn’t benefited Russians, and Mr. Putin is a ruthless dictator with contempt for human life, including the lives of Russians. The Russian opposition he represses is “liberal” not in the sense of being leftist but of favoring freedom. His opposition to the North Atlantic Treaty Organization isn’t antiglobalist but anti-Western and anti-American.

Still, that so many leading America-firsters are parroting the Kremlin’s narrative suggests the movement has taken a dangerous turn. The reasonable goal of reducing military adventurism has regressed toward extreme isolationism, producing a self-described antiwar movement that preaches peace while callously ignoring war crimes.

Mr. Shapiro is an investigative journalist who has reported on Russian affairs. He served as a senior adviser to the U.S. Agency for Global Media, 2017-21.