Opinions Can't Be Wrong

I absolutely hate it when people say an opinion is wrong. Not only is what their saying simply obnoxious but it's also incorrect. An opinion does not have the ability to be wrong, you can not have an opinion that is either right or wrong.

A quick definition of opinion is: " a belief or judgment that rests on grounds insufficient to produce complete certainty". If that definition is true than how can someones opinion be wrong if it is based on something that cannot be proven?

I know several people who have gotten big fat ZEROS on papers because the teacher has said "Wrong Opinion." They, of course, went to the teachers claiming several of the same arguments I say here and the teachers crushing response is often "I'm the teacher, what I say goes." Aren't teachers supposed to help us learn? Not put our opinions down without even thinking.

I just find it blasphemous to even consider saying this to someone. I just don't get what they're thinking. I find it completely alright to disagree with someones opinion but that, in no way, makes theirs wrong.