Medically retired usually means:
1. A player can no longer safely play. Often neck or heart issues.
2. Guy did everything he was supposed to do, but just wasn't good enough. He gets to stay and graduate from the university. The school benefits because they honor the scholarship to avoid bad PR and free up a scholarship.
This professor is uninformed and morally outraged for his own benefit. The goal here is to attack football, not help players. The professor's status in the university should be obvious if their job is instructing courses athletes are taking.