Teachers are supposed to not only teach, but inspire. So all should be accepting, patient, and generally, kind. When you get a teacher that embodies none of those things, it's definitely a cause for concern.
We can all look back and remember that one teacher we absolutely despised. Often they're just boring or slightly rude, and although they pissed us off back in the day, they didn't completely ruin our school experience.
Well, some people had the absolute worst teachers EVER. Some would even say evil. They had teachers that were rude, racist, homophobic, sexist, and just all around terrible and inconsiderate. They 100% scarred some students for life.
Not only were they just generally horrible, but they said specific things that were pure evil. Like, deserved to be fired evil. Seriously.. HOW WEREN'T ALL THESE TEACHERS FIRED?!?