Professors and teachers are still human and they can make mistakes. It doesn't make them look stupid, dumb, or anything less than human. If you feel as if your grade is too on a certain exam paper, we are in fact encouraged at school to challenge it, non-confrontationally, of course. It is a good idea to keep it civil and pose the challenge as a question, asking the teacher for justification.
This could just get you an even lower grade or detention. The professor is must smarter than you are so I would just let it go. But hey if you want detection you go get that detiontion. I am not even going to try stopping you. No offense either, okay?