I agree with you that Email may not have a case if the whole event is as what he described. However, I will not draw this conclusion since I don't know all the details. Does Email overreact to what had happened to him? Is the Professor only against him, or is he unfair to many other students? Does the professor have a long history of being unfair to students?
I feel the topic we are discussing here is not simply whether Email should bring the lawsuit, but whether a Chinese should speak out once he suffers unfair treatments. Legal help is one way to seek for relief. It doesn't mean that we should file lawsuit for any trivial unfairness, but we really should learn how to protect our legal rights once they are violated. It is not a shame to go to the court. US society encourages such conduct as long as one doesn't make up all the supporting facts. In many cases, the person who sues not only gets relief for his personal damage, but helps many others who are similarly situated.