Introductory courses for most sciences are based on unrealistic assumptions, and for such courses in economics to do this must mean economics has become a science.
On a serious note, it doesn't seem as if some students have much choice:
Harvard students have reasons to be angry. While they're taking notes on the inefficiency of price ceilings,
the Justice class nearby is arguing about Rawlsian ethics. The latter is what was advertised and what applicants dreamed of. And don't dismiss everyone going to Harvard as doing it for the degree - financial aid means there are disadvantaged students who wants the education. Connections aren't easy to make without academic merit, either.
One response gets the central problem when it says "One lesson from the first day of Ec 10 ... is learning to separate positive questions from normative ones." But the study of economics cannot choose between one or the other. Instead, the way the course is taught can be changed. Maybe intro econ can be taught in a "critical" manner by chronicling economics today as the product of economists' critiques.
