Victor Davis Hanson regresses to almost 400 BC and finds examples from history that teach us today.
My favorite example of castigating idealism is far older and from fourth-century B.C. Greece. By the 370s B.C. idealists were firmly in control of the government of conservative ancient Thebes, and turned an oligarchic Boeotian Confederacy into a real democracy. Convinced after their victory at Leuktra (371 B.C.) that a wounded Sparta was still a perennial threat, the new Boeotian democrats mobilized a Hellenic coalition of the willing to drop the old realist idea of containment or of just waiting for Sparta to attack.Those who don't learn from history are doomed to repeat it.
Thus they embraced the preemptive act of invading Sparta and freeing 250,000 Laconian and Messenian indentured serfs or helots ("those taken"). The preemptory invasion was aimed at bringing freedom and democracy to Greeks heretofore deemed less than fully Hellenic and thought incapable of self-governance. Indeed, over the past century thousands of helots had been arbitrarily executed and routinely tortured and humiliated by their Spartan overlords. The Boeotians thought that by freeing the helots and creating autonomous democracies on Sparta's borders they could remake the Peloponnese and end the old pathology in which a professional Gestapo-like military coerced their neighbors and meddled abroad, while fed and supported by a veritable nation of serfs.
The subsequent successful invasion led by the general Epaminondas was one of the few military operations of the ancient world that had real elements of idealism. Yet the circle around Epaminondas was also suspected of being influenced by the Pythagoreans, zealots who had fallen under the spell of the subversive and dangerous teachings of Pythagoras. The latter purportedly had promulgated weird notions, ranging from the equality of women to vegetarianism, and his work seems to have influenced Plato. Perhaps, Pythagoras was an ancient bogeyman not unlike the contemporary Leo Strauss, and was used to explain the otherwise inexplicable fact that the Boeotians of all people went into the heart of darkness to free the people of the Peloponnese.
One last thing about such appreciation of idealism in foreign policy: After Epaminondas emasculated Sparta, liberated the helots, and fostered a democratic Peloponnese, the Thebans, far from hailing the hero, put the returning commander on trial for usurping his prescribed tenure.