Why doesn't my cat like my one friend?

My cat, Onyx, loves me to death. He likes everyone else, except men, and this one person. I have no clue why. My friend will come over, and while Onyx won't run from her, he won't appreciate her petting him, and he acts like he doesn't hear her. I've heard that cats are very good judges of character, and that they can tell a true friend from a false friend, could this be true for Onyx?