There are at least two ways to argue against going to such a university.

First, you can say that you would put yourself at a disadvantage by going to such a school if you intended to be honest yourself.  You would be competing in all your classes against a number of students who would feel that cheating and plagiarizing was perfectly acceptable.  Your grades, though obtained honestly, might look bad compared to theirs and you would hurt your chances for things like jobs or graduate school admissions.

Second, you can argue that your diploma might not mean as much as it should.  If your university had a bad reputation, employers or graduate schools might not put much stock in your diploma.  They might assume that you yourself cheated your way through school.  You would be guilty by association and your future would be jeopardized.