On relationships with students

I work in a small, relatively unproductive, unnoticed philosophy department. One of our tenured faculty members is in a committed relationship with one of his female students. He is her thesis and teaching supervisor. The relationship began shortly after she joined the department. My department tacitly condones this relationship by ignoring it. I find my department’s tacit condoning of this situation offensive and sexist. 1)It is unfair to her. As an Associate, he has all of the power. 2)It is unfair to the other students in the program. There is no doubt or question that she has and will receive special treatment. 3)It is unfair to other faculty. How can we be expected to grade her without bias? 4)It sends the wrong message to the few female students in the department. I have personally witnessed public displays of affection between the two. I think that it not only sends the wrong message to those of us within the department, but also to other departments.