Much the same as environmentalist's faith in ecological harmony being constrained by the fact that there is no such thing. The environment isn't harmonious but rather is starkly violent, hyper-competitive, and ever changing. What they are actually pursuing is a nostalgic return to childhood or primitivism, but not balance or harmony.
Then of course, there are the myriad of utopian political visions such as communism, multiculturalism, egalitarianism, etc. all of which suffer from the basic truth that human beings are not infinitely malleable. Hence their tendency to drift into authoritarianism in an attempt to force that change that our natures resist.
How about the neo-conservative utopian vision for the middle-east? Somehow, in spite of culture, race, religion, and history we could turn them into a nice, happy, pro-western democracy... and all we need to do to topple the dominoes, is strike Iraq. Worked out about as well as any other plan rooted in utopianism.
What is John McCain's utopianism? A frightful combination of 60's trauma induced faith in interventionism coupled with a new-age egalitarianism.
John McCain's foreign policy is rooted in the belief that American military influence can maintain an international equilibrium or harmony if you will. Somehow, we can prevent all wars, invasions, political uprisings, and genocide if we just try hard enough and have enough troops. That is the bold, imperial dream that defines his foreign policy and like any other utopian vision, it's rooted firmly in hope rather than fact. This kind of irrational disconnect from reality doesn't bother me much when I hear it from an athlete or motivational speaker but it's a bit more troubling when spoken by someone who might very well one day control the largest nuclear arsenal in the world.
I hate to take a cheap shot at the man but I've begun to suspect that his time spent imprisoned in Vietnam has left him permanently removed from reality, and stuck in his own vision of the world. He spent the worst years of the war in a prison camp being tortured with only his commitment to his duty to protect. He had to believe that the war was just or he wouldn't have been able to survive it. He didn't endure the most disillusioning years of the war as his fellow Senator's Hagel, Kerry, and Webb did. Instead he spent those years necessarily reinforcing the noble and just cause that lead to his imprisonment and torture. Couple that with his fathers belief that had the he been allowed to utilize total war, then the U.S. could have emerged successful. That, and not the facts of reality today, are what shape McCain's perfectionist foreign policy. While he may be a brave and decent man, he is also damaged in a way that makes him incapable of having a realistic view of the world. For him, the interventionist policies of the past sixty years are not failures, they just need more troops or more time and nothing will ever convince him otherwise.
The world is a chaotic and dynamic place with different nations, races, religions, corporations, and NGO's all vying for resources, influence, and power. It is an ever changing world where adaptability is second in importance only to having a keen sense of danger and the rational pursuit of our national interests. This requires a level of objectivity that the Arizona Senator is tragically incapable of.