There is some truth to all of the responses. However, there are circumstances where no matter what action you take, you could end up in a miserable situation you could not have anticipated. It takes both sides to cooperate for a win-win. Sociopaths will not care at all about you and they prefer control/power.
1) Always always document: keep e-mails, write down incidents & conversations even if you are not the target.
2) Report to management in a timely manner. However, remember that they & Human Resources will protect the company and themselves.
3) Even if you do everything in a positive & professional manner, some people know how to twist it all into negatives.
4) Read the book "Mobbing: Emotional Abuse in the American Workplace." There are also books on "toxic" people. You will learn why most of the reasonable tactics won't work. They may actually backfire.
5) If necessary, file a complaint with the EEOC. However, the legal system is not educated in workplace bullying. You need to learn the legal lingo and have money to spend on a lawyer on a contingency basis. Learn before you spend.
6) Support Healthy Workplace Advocate organizations. Bullying in the workplace is illegal in several countries. It is psychological violence, which can have devastating effects on your health, your career, your family, and your finances.
7) Leave before you are injured! PTSD, depression, & anxiety are serious medical conditions, which can take years and money from your life.