On Jan. 29, 1981, barely a week into Ronald Reagan’s presidency, the world got a no-nonsense education on how Reagan’s America would differ from that of his predecessor. During the first press conference, ABC’s Sam Donaldson asked the new president about Moscow’s aims and intentions. Throwing diplomatic double-speak to the wind, Reagan calmly explained that the Soviet leadership had “openly and publicly declared that the only morality they recognize is what will further their cause, meaning they reserve unto themselves the right to commit any crime, to lie, to cheat.”

Reagan continued, explaining that the Soviets considered their relativistic behavior “moral, not immoral.” This was something that the United States needed to “keep . . . in mind” when doing “business” with Moscow. The assembled Washington press corps responded with what National Security Adviser Richard V. Allen described as “an audible gasp.”

Reagan’s rejoinder was deemed a crass outrage. The journalistic elite sniffed, Who is this Neanderthal? A Washington Post editorial lamented the “indiscriminate quality of some of the things being said.” This sudden “good-vs.-evil approach risks missing what legitimate opportunity for honorable accommodation there may be.”

In the ensuing weeks, America’s leading journalists—perplexed, offended—repeatedly pressed the new president for clarification. And so Reagan would clarify, again and again, saying of the Soviet leadership: “They don’t subscribe to our sense of morality. They don’t believe in an afterlife; they don’t believe in a God or a religion. And the only morality they recognize, therefore, is what will advance the cause of socialism.”

All this was too much for CBS Evening News. CBS’s grand old anchor, Walter Cronkite, got the opportunity to confront Reagan during a March 3 interview. Cronkite told Reagan that the president’s views seemed too “hard line toward the Soviet Union.” He noted that “there are some who . . . feel that you might have overdone the rhetoric a little bit in laying into the Soviet leadership as being liars and thieves, et cetera.”

Reagan did not back down. He noted that he had merely responded truthfully to a question from a reporter about “Soviet aims.” On that, said Reagan, “I don’t have to offer my opinion. They [the Soviets] have told us where they’re going again and again. They have told us their goal is the Marxian philosophy of world revolution and a single, one-world communist state, and that they’re dedicated to that.” The president harkened back to the Soviet version of morality: “Remember their ideology is without God, without our idea of morality in a religious sense.”

Cronkite seemed befuddled and bothered. He described Reagan’s words as “name-calling,” and he expressed concern that this would make “it more difficult” to sit down with Leonid Brezhnev and the Soviet leadership.

Yet Lenin declared in 1920: “We repudiate all morality that proceeds from supernatural ideas that are outside class conceptions. Morality is entirely subordinate to the interests of class war. Everything is moral that is necessary for the annihilation of the old exploiting social order and for uniting the proletariat.”

Reagan had it right, and he took that insight, and self-assurance, into a two-term presidency where his goal was to win the Cold War and defeat that evil system.

Alas, there was a golden moment at the end of that first press conference, unseen by the public or cameras. It was shared years later by Richard Allen. When the press conference was finished, Reagan, who recognized the weight of what had happened and was unfazed, called over to Mr. Allen and asked, with a grin: “But Dick, the Soviets do lie and steal and cheat, don’t they?”

“Yes sir, they do,” Mr. Allen replied. Reagan smiled and said, “I thought so.”

In January 1981, the world needed a leader who indeed thought so, who dared to say so, and who was willing to do something about it.

Mr. Kengor, professor of political science at Grove City College, is author of “The Crusader: Ronald Reagan and the Fall of Communism” (Harper Perennial, 2007) and “Dupes: How America’s Adversaries Have Manipulated Progressives for a Century” (Intercollegiate Studies Institute, 2010) .