Reader query: how to help?

A reader writes:

So, I/the rest of my cohort are facing a difficult issue: a male faculty member has two advisees in my cohort, a man and a woman. It is obvious to the rest of us who are not his advisees that he treats the male student *much* better than the female student. Yesterday we all did presentations of our research for this faculty member (as part of a dissertation seminar). Her presentation was very good, just way too long and thorough. After she finished, the faculty member proceeded to go off on her for a good fifteen minutes, in front of the rest of us (her peers). Stuff like “this isn’t philosophy” and “this all has to be gotten rid of,” the latter of which he sort of changed his tune about over the course of his rant. It was intense. Had I been the student on the receiving end, I would have cried. I’m amazed that she didn’t.

My question is: this is plainly inappropriate behavior, but what can we (as her fellow grad students) do about it? I mean, content of the presentation aside, what seems inappropriate was to dress a student down in front of her peers and to do it in such a harsh manner. I’m just worried that, because this faculty member is well-regarded in the department, that if a few of us were to tell someone about this that we at worst would not be believed and at best there would be nothing that anyone else could do.

So, for readers: what can fellow grad students do to support a grad student in an abusive advisor relationship?