How can I deal with a Bias teacher?

Why are you approaching him in front of the whole class? That's what office hours are for. Trying to use up class time or time right before or after to discuss a personal issue will get you yelled at by most professors for being inconsiderate. Engineering is a very quantitative field - if you got it right and it's marked wrong, you can prove it's right. So if your paper is marked down unfairly, that's very easy to prove, and if he doesn't correct it then you can take it to the dept head. But make sure you're right first. Minor mistakes do build up; it's not unjustified to take off points for that. Compare to other students to find out how the grading worked - usually it's pretty straight-forward.