Insulting email from another graduate student I'm first year international graduate student in US and recently I have received an insulting email (for example including "be thankful and keep your mouth shut") from a domestic student who is my teammate in a class project. The email was a follow up to my debate with another teammate, however there wasn't any context for anything like that (I consider all of university email as public records and I'm careful about what I write), and initial conflict was going to be resolved with few email exchange. When I brought up the issue to the class professor, he (the student) claimed that he was angry because of my position in the debate and he was defending the other team member, but overall he (the student) defended his email. The professor tried to calm us down and avoid escalating the conflict.

I have experienced similar but milder situation with other domestic students and in one case a young professor as well. The general hostility pattern is that, they expect me to keep my mouth shut and be second class citizen. I have heard from other international students that our small city/university is not a good place regarding this issue. My question is, can I do anything about it?
I cannot give you advise on what to do in this situation as it depends strongly on the context, and you cannot give that information on an open forum like this. 

However, I can make one comment: in general I would never try to solve such a conflict through email. Email is great, but when you sense that a conflict might start you immediately need to stop using email and try to speak with the person directly. Small misunderstandings that are easily resolved in face to face communication tend to get blown out of proportion very quickly in an email conversation.