Who says it hasn't been? In general, universities and non-profits and companies don't disclose private reports of abuse or harassment. Who says MIT, the FSF, and GNU Project haven't all been getting private reports in addition to the people tweeting and blogging about their misadventures with RMS?

And regardless, this behavior has apparently been going on for decades without anyone taking action. Can you blame people for thinking that "the right channels" aren't working?