It's quite a while since I was at university and back then there would have been very little chance of a professor being fired that easy or on those grounds.
That said, back then, the system was very fair. Students were treated with respect and often given benefit of the doubt. There were appeals mechanisms in place if students failed and they could do so if they thought they had good reasons to appeal, and so on.
Looking in at much of academia these days I see a volatile, messy quixotic buisness and I'm glad I'm not there. (It's still not fully clear to me how things have gotten so off the rails in recent years.)
In direct answer to your question I'd repeat what I said above with respect to my university experience. The system should be fair and flexible and students should always be given a chance to do better next time.