Everything I hear from other NATO members is that the U.S. has become the obstacle, and an explanation is required. Allowing Mr. Putin to keep an inch of Ukrainian soil after bombing civilians should be unimaginable. Conceding large areas of eastern Ukraine to the invader in exchange for a cease-fire would only give Mr. Putin time to consolidate and rearm for next time—and there will always be a next time. No peace deal should weaken the strong sanctions that have finally arrived, eight years late.

The only drawback to the end of the Cold War was the loss of the moral clarity provided by a clear and present evil. Aside from a handful of fellow travelers and useful idiots, even Ronald Reagan’s critics couldn’t doubt the accuracy of his calling the Soviet Union “an evil empire” in a 1983 speech, as startling as it was to hear a politician speak so plainly in moral terms. It was also a tonic for those of us inside the Soviet Union to hear what we knew to be true said aloud by the leader of the free world.

Mr. Biden’s age may be a negative for some, but he remembers the Cold War. Gaffe or not, his remark reflected accurate instincts: Mr. Putin must go. But the war in Ukraine is also a distraction from his flailing domestic agenda. It’s hard to talk about economic and social issues in the U.S. when a real war is leading the news every night.