I think there is most definitely a line where there can be no reasonable or safe way for someone to try and communicate privately and should definitely go to a third party to sort this out as a first step. I've heard of stories in academia where freshmen are literally physically cornered by staff, where someone is being stalked by a student who is unstable, where a student is physically threatened, where a student is offered extremely inappropriate quid pro quo for grades/research opportunities, etc.