I agree that it limits the criticism one can lob at the Bush administration. But those limits aren't too tight. Consider the difference between using American power with bold assertiveness and using a lighter touch. If Bush were to have cultivated more goodwill among our allies and potential allies, there is every reason to believe that their leaders and citizens would feel more positively toward the US and the Iraq war. It wouldn't necessarily turn the tide; it would just reduce their feeling of powerlessness, which makes them want to oppose anything the US does.
What Bush chose to do was to throw around America's weight, make threats, chastise other leaders, show little interest in their input outside of formal procedures, and repeatedly stress how unimportant everyone else is. Did he have some valid points? Yes. But we want to be effective, not self-righteous. Human relations, one-to-one and mass-scale, require stroking, smoothing, respect, understanding, and empathy. None of which has been in evidence, which is making it unnecessarily difficult for the US in the war and its other dealings (Kyoto, ICC, etc.).
For a sample of this reasoning, check out this Slate article, "Turkey Shoot: How Bush made enemies of our allies"..