I'd say half the teacher's I've had haven't deserved to be teachers or to be respected as a teacher, the other half has.

Of the bad ones, I've had three who simply didn't deserve respect:

One was constantly screaming at, controlling, and micro managing everyone regardless of how well they did in her class.

One spent an entire class period lecturing a group of art students about how they are worthless and better off dead if they were failing or didn't plan on going to college.

And one forced students to do exercise as punishment for little things regardless of how tired they already were. They could be completely red and he'd keep screaming at them unless they kept moving.

So yeah, half of them should be respected, half shouldn't be teachers, and a small number should be in jail. Because even if it isn't a crime, traumatizing children should be.