Last month, the Russian parliament mounted an unusual art exhibition with subjects ranging from the Soviet dictator Joseph Stalin to a sentimental image of a kitten. They had been produced in prison by Viktor Bout, serving 25 years in America.

History has shown that a sideline as an amateur artist is not much guarantee of moral integrity. Bout, known as “the merchant of death”, was the world’s most notorious arms dealer, selling weapons to rogue states, rebel groups and murderous warlords in Africa, Asia and South America.

That, for many, was what made his release on Thursday in a prisoner swap for US basketball star Brittney Griner difficult to stomach. Joe Biden has done a deal with the devil. But he may also have saved a woman’s life. As the president found in Afghanistan, the big decisions are seldom morally clearcut.

On the credit side, Griner’s release is spectacularly good news. She was arrested in February after vape canisters containing cannabis oil were found in her luggage. Against the backdrop of war in Ukraine, her nine-year prison sentence was wildly disproportionate. Her transfer to a penal colony, with its promise of sexism, racism and homophobia in medieval conditions, raised fears for her survival.

But on the debit side, despite Vladimir Putin’s effort to portray Bout as painter and classical music lover with a sensitive soul, the arms dealer has blood on his hands. He armed militias in Sierra Leone, the Liberian war criminal Charles Taylor and the Taliban in Afghanistan. His life helped inspire the 2005 Hollywood film Lord of War, starring Nicholas Cage.

Bob Menendez, chairman of the Senate foreign relations committee, captured the ambivalence in a statement on Thursday. The Democrat welcomed Griner’s release as a “moment of profound relief” but warned that “releasing Bout back into the world is a deeply disturbing decision”.

He added: “We must stop inviting dictatorial and rogue regimes to use Americans overseas as bargaining chips, and we must try do better at encouraging American citizens against traveling to places like Russia where they are primary targets for this type of unlawful detention.”

Michael McCaul, the top Republican on the House of Representatives foreign affairs committee, also expressed relief but warned that “trading Viktor Bout – a dangerous convicted arms dealer who was in prison for conspiring to kill Americans – will only embolden Vladimir Putin to continue his evil practice of taking innocent Americans hostage for use as political pawns”.

Predictably, there was a less measured response from Donald Trump’s wing of the Republican party. Some cried foul over the fact that while Griner was coming home, the former US marine Paul Whelan, convicted in 2020 of spying, will remain in a penal colony.

Cory Mills, an Afghanistan and Iraq war veteran and congressman-elect from Florida, tweeted: “Biden clearly showed his priority is celebrities over veterans. I guess Brittany’s basketball career in WNBA was more important than Paul Whelan’s service to our nation as a marine.”

In a phone interview from his penal colony, Whelan told CNN he was glad Griner had been released but “greatly disappointed” that the Biden administration has not done more to secure his own freedom. According to the White House, Russia is treating Whelan’s case differently because of his espionage conviction and was not willing to include him in the deal.

Not even Republicans, however, were accusing Biden of being “soft on Russia”, given his success in rallying the west against Putin in Ukraine – a vivid contrast from Trump’s embrace of the autocrat. The war has been unusual in its lack of ambiguity between right and wrong.

After meeting Griner’s wife, Cherelle, in the Oval Office, it was clear Biden had no doubt he had done the right thing despite the understandable ethical qualms.

“It’s my job as president of the United States to make the hard calls,” he said. “And I’m proud that, today, we have made one more family whole again.”