Feminists know for a fact certain things that no reasonable person can say with certainty. For example, they know for a fact the exact number of women actually raped each year. They know for a fact the exact percentage for underreporting of rapes. And they know for a fact the exact percentage of false rape claims. (The "facts" that the feminists "know" do not comport with even reasonable estimates proffered by objective observers, but that is beyond the scope of this post.)
But when they are confronted with irrefutable proof that no rape occurred, they lose all ability to speak with feminist infallibility and quickly and solemnly proclaim that "no one will ever know for a fact what happened in this particular case."
This, of course, is intended to suggest that a rape very well might have been committed. It is a common tactic of theirs (we saw it in the Duke lacrosse case, we see it now in the Hofstra false rape case, and we've seen it in numerous other less well known false rape cases), and it is dishonest in the extreme.