While it is true that Kutztown State may actually be more rigorous than MIT, it is not unreasonable to make the assumption that certain schools (e.g., MIT, Princeton, Stanford, Harvard, etc.) are more rigorous than just about most other schools.
The alternative is to assume that all schools are completely equal in rigor. But common sense tells us that schools that are more selective (i.e., those with higher average SAT scores) tend to be more rigorous because:
Smarter and/or more hard working peer group ===> Being graded against the best & encountering tricky test problems that are meant to spread the distribution of grades.
It seems more unfair to me to assume that all schools (and all majors for that matter) are equally rigorous when we know that is not the case. Assuming some schools like MIT are more rigorous than others may, in some instances, actually be a false assumption (Kutztown State might actually be more rigorous than MIT), but in most cases will be a valid assumption to make.