Gay marriage good for landlords

Q: I’d like to know if I’m risking a lawsuit if I refuse to rent an apartment to two men who say they are married. I have nothing against gays or lesbians, but I believe that marriage is not appropriate in this situation. These applicants tell me they are legally married (in Massachusetts), and that if I turn them away for this reason, I’m discriminating against married people. In my state, gay and lesbian couples are not allowed to marry, but I understand that in Massachusetts they can do so. What are my rights in this situation? –Anita B.