SAN FRANCISCO - Political epiphanies can occur in unexpected places. For Riki Dennis, a 35-year-old humanities student who is transsexual, it was the women's room at a rest stop on Highway 101 north of Santa Barbara. "The boyfriend hit me, even in mellow California," said Ms. Dennis, who was in the early stages of becoming female when she was assaulted by a stranger after using the women's room. "I said, 'Sir, I have no designs on your girlfriend.' I just want to use the bathroom." Ms. Dennis, whose lowish voice is now the lone betrayal of her birth sex, is...