Well, I don't know about a lawsuit, as I'm no lawyer (though I do know that wrongful termination suits don't have to have anything to do with race, sex, or religion, so there might be something that can be brought to bear in court). However, most large companies have regulations covering hostile workplace environments that in no way involve race, sex, or religion, and there's a lot of layers over a DM's head that live to do things like enforce those regulations. This sounds like a job for Ombudsman Man!