Just when it looked like the level of dialogue between Washington and Moscow couldn’t sink any lower, there goes President Biden calling the Slavic Darth Vader, President Putin, a “crazy SOB” — and the Kremlin serving up sassy ripostes. It is a development at once alarming and surreal, because February’s reality belies the conceit that only the leaders’ slightly dented egos are at stake. 

During a fundraiser on the Coast, Mr. Biden said, “We have a crazy SOB like Putin and others, and we always have to worry about nuclear conflict, but the existential threat to humanity is climate.” Beyond the president reckoning the human race is at risk of expiration due to the weather, the more unsettling forecast is that invective between Washington and Moscow is now likely to grow. 

Russia’s state-owned news agency, Tass, reports that Mr. Putin’s toothy response was this: “I said that for us Biden is preferable as president” to President Trump, “and judging by what he has now said, I am absolutely right.” He added, according to the same agency, “Of course, he couldn’t have said to me, ‘Vlad … thank you, you help me a lot.’”

Russia’s always colorful foreign ministry spokeswoman, Maria Zakharova, also chimed in, writing on her Telegram channel, “The next time Joe Biden uses the term ‘crazy son of a bitch,’ he should remember that Americans best associate him with his own son, Hunter Biden.” 

The generally more even-keeled Kremlin spokesman, Dmitry Peskov, also weighed in: “The use of such language against the head of another state by the president of the United States is unlikely to infringe on our president … but it debases those who use such vocabulary,” he said, adding that the remarks were “probably some kind of attempt to look like a Hollywood cowboy.”

Salty language is one thing, but relations between Moscow and Washington, and with the West in general, do appear to be plunging toward rock bottom. The untimely demise of the imprisoned Russian opposition leader, Alexei Navalny, under highly suspicious circumstances last week only made matters worse. Mr. Biden has previously referred to Mr. Putin as a thug and a war criminal, so the comments made at San Francisco should elicit no particular alarum. 

It does seem, though, that the Kremlin, when not issuing saucy statements via the state-run propaganda dispensaries, is ratcheting up the rhetoric — and some of it might have raised more attentive antennae at Washington. In an interview with Russian state media this week, Russia’s former president, Dmitry Medvedev, takes aim at the West with his signature dark élan.

Mr. Medvedev has previously disparaged European leaders as “a pack of barking dogs from a Western kennel” and “a motley pack of grunting pigs.” This week he said that when relations with Europe “normalize, the vast majority of current politicians in the West will fade into political oblivion. And about some I will say as I have been saying lately: Some of them will simply die.”

Mr. Medvedev hinted that Moscow still has the Ukrainian capital in its sights. He said that “Kyiv is a Russian city, and from there comes a threat to the existence of Russia, because it is controlled by an international brigade of opponents of Russia.” In the same breath he stated that Russia needs “to create the necessary protective cordon that will protect against all kinds of encroachments.”

He spoke of “not only shelling, but also active offensive operations.” The parts of Ukraine that Russia now controls are nearer to the Black Sea port of Odessa than to Kyiv, which Moscow failed to take roughly two years ago. For Mr. Medvedev, as he reminded his Russian interlocutors, “About Odessa, I can simply say: Odessa, come home! This is our Russian city.”

Those are likely Mr. Putin’s thoughts exactly. As for Mr. Biden, some might find his candor in respect of his Russian counterpart refreshing. It is a nice break that he isn’t, for the  moment, leveling insults at one of our own, such as when he called Fox News’s Peter Doocy a “stupid son of a bitch.”