Because, it seems, the people she is scapegoating deserve it. A common charge is that her essay was just a publicity stunt, that with it Dworkin not only had succeeded in obtaining sympathetic attention for her book but had perhaps deliberately told a questionable story, so that when challenged, she could continue to play the feminist martyr whose agonized cries are never believed. But most think that idea is far too cynical. Bright wrote a surprisingly sympathetic column on the issue. I would rather have sympathy for that version of events than to believe she is maliciously making the whole thing up.
People have to know that they are telling untruths in order to be justifiably called liars.
Many character disorders, including borderline personality, involve 'lying' and not knowing one lies. There is no question that something happened to Dworkin last year, something that has devastated her psychologically, and it seems that the disbelief of even her closest associates has been a significant part of her distress. In her essay, Dworkin writes that she called her feminist gynecologist in New York a few days after the incident. She says the doctor told her that a gynecological exam would prove nothing one way or the other and that being called on a Sunday had made her decide to get an unlisted number. The doctor's coldheartedness toward a patient she had treated for 10 years is not explained further.