Intro courses and liberal arts courses should force people to think and many do learn to think. There is plenty of time to learn about testing and quantifying ideas. Intro to econ is about learning to think through systems with many variables. Its about wraping your mind around concepts. There is value in asking the question... does raising taxes raise revenue, and understanding the answer is --- it depends in part on whether you are on the left side of the curve (near 1% or on the right side of the curve near 100% taxes. Very few people understand curves and systems... but plenty of people can quantify things. Have we even had one person other than Paul Ryan - media or politican discuss taxes and revenues intelligently? How many leftists understand that sometimes cutting taxes raises revenue and vice versa?
If I were Mankiw, I'd have to be laughing to myself that the students who walked out didn't even understand the difference between microeconomics, which is the topic of his first semester class, and macroeconomics, which comes later in the year. Nor do they seem to understand that Mankiw is of the Keynesian persuasion himself, albeit of the school that prefers a larger portion of its government stimulus in the form of tax cuts, rather than direct government expenditures. The fact that these students (although one hesitates to use this word for them) think that "Keynesianism" equals "more Obama stash money being spent" just shows how thoroughly indoctrinated they are, without their even knowing it, of course. Honestly, these young cretins are beyond parody. It's gotten so that almost anyone under the age of 30 should be seen and not heard. The world is far too complex for anyone of that age to have even a smattering of the knowledge necessary to have an educated opinion. Certain exceptions apply, of course, but I'm speaking in general.