Have we reached the point where online trolling and harassment, already a familiar scourge of the internet, are starting to erode freedoms we took for granted long before the advent of the internet? For the latest evidence the answer may be "yes," look no further than the recent firing of a tenured professor at Marquette University.

To recap a series of events that deserve to be examined in greater detail (an excellent source for such detail is Conor Friedersdorf's write-up at The Atlantic), an undergraduate student at Marquette was unhappy with the way his grad-student teacher handled a philosophical question concerning gay marriage. She suggested they speak after class, which they did. Their exchange grew increasingly heated, with reciprocal accusations of offensiveness and inappropriate speech, which culminated in the teacher's statement that the student can always drop the class if he can't keep himself from making "offensive" comments.

The student, without the teacher's knowledge or permission, recorded the conversation, and passed it on to a tenured professor sympathetic to his politics. The professor published a piece on his blog attacking the grad student teacher by name, and accusing her of using tactics "typical" of her political perspective to stifle debate. This triggered a wave of online harassment of the grad student teacher, who has since left Marquette to complete her Ph.D. at another university. Meanwhile, the university administration first suspended and then terminated the tenured professor's position for unethical and unprofessional conduct in publishing his original blog post.

Who is the villain here? Well, the grad student teacher probably didn't handle her interaction with her student optimally. The student probably acted unethically in recording the interaction without the teacher's permission. The tenured professor probably acted inappropriately, and certainly in an uncollegial manner, in attacking the grad student teacher publicly rather than communicating any concerns through official departmental or administrative channels.

But students have always been frustrated by teachers, suspecting that they treat students differently based on the congeniality of their opinions. Teachers have similarly been frustrated by student complaints. And academics have been insulting each other in public in the most lurid terms since the time of Plato.

It's still a somewhat new experience, however, to be subjected to harassment by an anonymous and unaccountable online mob. It's horrible enough when journalists are subjected to truly psychopathic levels of abuse. Nobody deserves that kind of treatment — but journalists do, at least, aim to be known, read, and responded to. A graduate student has no reason to expect that someone would hang a pixelated target on her face.

Absent the mob, the initial recording by the student would likely have been of interest only to the philosophy department's faculty. "My teacher wouldn't let me make a valid argument" is hardly a page-one news story. Absent the mob, the professor's blog post would similarly have raised few hackles; it would have been no worse a breach of etiquette than saying the same things out loud in the faculty lounge.

That mob is what transformed this situation from a routine and largely uninteresting ivory tower spat into a dark precedent for academic freedom. Which is what this is. It has become all too difficult to draw clear contours around the new implicit restrictions on academic speech, which would appear to put professors in the distinctly odd position of being less free to criticize one another in print than civilians not crowned with the blessing of tenure.

And, ironically, the original complaint of the student — that he wasn't allowed to discuss a particular topic because the teacher feared he would offend other students — is likely in part a consequence of the toxic debate environment the online mob has helped create. It is probably not an accident that demands for "safe spaces" and ever-expanding definitions of harassment are features of the same landscape as 4chan and Reddit.

It's difficult to identify actions that might be taken to rein in the mob that wouldn't represent a more serious abridgment of freedom than the existence of the mob itself. Hate speech laws present obvious opportunities for abuse, but more libertarian-friendly strategies, like an expansive invasion-of-privacy tort, raise similar fears about a chilling effect on legitimate debate.

But if we want to secure the blessings of liberty for ourselves and posterity, we'd better figure out how to do it. When the streets seem unsafe, people retreat to gated communities. And you won't find the most vigorous political and philosophical debates in the kinds of places where everybody has to paint their mailboxes the same color.