[anatoly]

Consider that these people updated, you just don't share their conditional probabilities. In particular, they might think that P(response by MIT as given|harassment nonexistent or relatively trivial) is fairly high, given their understanding of or experience with the academic climate in the recent years, internal politics in academia, standards of institutional ass-covering etc. It's also notable (given that sexual harassment is a crime) that no involvement by authorities is described or even hinted at.

You do make a good point. "no harassment happened" shouldn't be the strong default belief (I'm not sure it actually is for many people here). But based on the statement and what is known about the relevant politics in academia, "serious harassment definitely occurred" shouldn't be one either.