How are you supposed to deal with a MEAN professor?

well the 1st thing I would do is find out who is getting A's and figure out their secret. Some prof's just cant be pleased and honestly at the graduate level, that's not so unreasonable. A prof teaching a graduate level cl should have high expectations. Secondly, you might ask the professor for time to talk to him one on one. And when you have the time, dont complain or talk about things being unfair. Instead, explain to him that you understand how difficult the material he is teaching is and ask him what you need to do to be successful in his cl. At that point if you do what he has told you to do then you can expect good grades from him. And if he gives bad marks while you are doing what he has told you, you can point out to him that you have done what he told you to do and it still is not working and he might see the error of his ways.