Paul Pillar rejects the idea that Eisenhower erred by opposing the Anglo-French-Israeli attack on Egypt in 1956:

Both Joffe and Doran exhibit the post hoc ergo propter hoc fallacy by implying that what they describe as the failed state of U.S. policy in the Middle East by the end of the 1950s, with expanded Soviet influence and the 1958 coup in Iraq, somehow flowed from Eisenhower’s firm line on Suez. That is not credible. It is hard to believe that a leader of Nasser’s charisma and rabble-rousing skill would have been any less able to stoke anti-Western Arab nationalism if the tripartite invasion had been allowed to stand. More likely, letting it stand would have made it even easier for him to do the stoking by providing an additional emotional cause about Western imperialism and subjugation of Arabs.

It’s also important to remember the overall international situation at the time. The Suez crisis was just a few years removed from the first use of collective security in Korea under the auspices of the U.N., and the Soviets had been crushing the Hungarian uprising. Had the U.S. endorsed flagrant acts of aggression by our allies after opposing them when they were committed by adversaries, it would have made a complete mockery of international law and contributed to undermining international peace and security. The more immediate danger of backing the attack on Egypt would have been to risk a major crisis with the USSR, which Eisenhower was doing his best to avoid.

Pillar continues:

Doran writes that after the Suez crisis the United States “was paying a heavy price for having broken the only immutable rule of a realist foreign policy: Support your friends and punish your enemies.” I know no self-respecting realist thinkers who would phrase their outlook in terms anything like that. They would instead echo the words of one of Britain’s most astute—and realist—statesmen, Lord Palmerston, when he spoke of having no permanent friends or enemies, only permanent interests.

Indeed, what Eisenhower did was to distinguish correctly between what was in the American interest (and perhaps what was in the best interests of our allies) and what the invading governments claimed was in theirs. Unlike some hawks nowadays, he refused to conflate American interests with those of other states, and he didn’t accept the idea that the U.S. was obliged to support allies when they were making a serious mistake.