"The campaign" is significantly ambiguous. There was a student protest movement. There are also a number of critics of Stock. These are not all one thing.

"can only be described as bullying" is also extremely problematic. First, it is unscholarly. In a discussion of academic freedom and related notions of freedom of speech, it is vital to be precise about actions which are merely unpleasant (e.g., refuting counterspeech), aggressive but still legitimate, individually bullying (e.g., a threat), and individually not-bullying but collectively so (e.g., a hostile environment). It's also important to distinguish responsibilities. If lots of people oppose you independently but vigorously, that might have the net effect of a hostile environment with none of the opposers being required to cease their opposition. (The employers might have some obligations to mitigate, of course.)