I once had a manager interview a black applicant, and when she was done, I said, "So how was she? Do you think she might work out?" And my manager just shook her head vigorously and said, "Oh, I'm not hiring people like that ever again. Not after the last one," meaning, the last employee was caught stealing from us on her last day (she had quit) and was also black. I was really upset by this and went to the district manager about it. The response I got was astounding. My district manager was white, an my manager was Hispanic. My district manager expressed surprise (if not outright disbelief in my complaint), because my manager was of "a different ethnicity too." You know, because only white people are racist, apparently. She talked to the manager, then talked to me and told me that my manager just felt "really bad about it," and everything was just fine. Of course, she never hired any black applicants after that, still.
I understand your frustration and it's very disconcerting to work with people like that and in that environment. Depending on the situation, you might just calmly tell you manager (or if possible, go to the next level up in authority like I did. Maybe you'll have better luck than I did), and that you're not comfortable with discussing politics at work, and that you're not comfortable with hearing ethnic slurs thrown around, either. You do have the right to work in a non-hostile work environment. If it gets really bad, keep your eye out for a new job, though I understand how precious jobs are in this economy (it took me months to find steady work when I returned to the States last summer, and I'm underpaid, overworked, and very over qualified for what I do).