Rebecca Journey, a lecturer at the University of Chicago, thought little of calling her new undergraduate seminar “The Problem of Whiteness.” Though provocatively titled, the anthropology course covered familiar academic territory: how the racial category “white” has changed over time.

She was surprised, then, when her inbox exploded in November with vitriolic messages from dozens of strangers. One wrote that she was “deeply evil.” Another: “Blow your head clean off.”

The instigator was Daniel Schmidt, a sophomore and conservative activist with tens of thousands of social media followers. He tweeted, “Anti-white hatred is now mainstream academic inquiry,” along with the course description and Dr. Journey’s photo and university email address.

Spooked, Dr. Journey, a newly minted Ph.D. preparing to hit the academic job market, postponed her class to the spring. Then she filed complaints with the university, accusing Mr. Schmidt of doxxing and harassing her.

Mr. Schmidt, 19, denied encouraging anyone to harass her. And university officials dismissed her claims. As far as they knew, they said, Mr. Schmidt did not personally send her any abusive emails. And under the university’s longstanding, much-hailed commitment to academic freedom, speech was restricted only when it “constitutes a genuine threat or harassment.”

The university’s 2014 declaration of free speech principles, known as the Chicago statement, has become a touchstone and guide for colleges across the country that have struggled to manage campus controversies, particularly when liberal students shout down conservative speakers. Scores of schools have adopted it.

But what followed for the rest of the academic year at the University of Chicago has tested whether its principles address a new, rapidly changing environment where a single tweet can rain down vitriol and threats.

The Chicago statement assumes that what takes place on campuses is “in good faith and that people have an interest in engaging the ideas,” said Isaac A. Kamola, of Faculty First Responders, which monitors conservative attacks on academics. But, he added, “the ecosystem that Daniel Schmidt is part of has no interest in having a conversation.”

Geoffrey R. Stone, a law professor, led the faculty committee that drafted the Chicago statement. He said that back then, the group was not thinking about how online threats could harm free expression — never mind this situation, where Mr. Schmidt simply posted a tweet with publicly available information.

Posting repeatedly, while knowing the response, might be harassment, said Erwin Chemerinsky, a constitutional law scholar at the University of California, Berkeley.

But, he said, “The hard question is, where is that line crossed?”

Mr. Schmidt seemed to understand that he stood right at the divide.

“Any other school would have probably expelled me by now,” he tweeted in March. “UChicago is the only top school that cares about free speech.”

Classes that explore whiteness have been taught in liberal arts departments for decades. Students explore how white people are treated as the norm, affecting, among other things, wealth and political power.

Dr. Journey’s syllabus included readings like, “How Did Jews Become White Folks?” by Karen Brodkin and “The Souls of White Folk,” a lesser-known essay by W.E.B. Du Bois.

Similar courses, though, have come under scrutiny by conservatives for being divisive.

“Like, what is this saying? That I’m a problem because I’m white?” Mr. Schmidt said in a TikTok video.

In an interview, Mr. Schmidt said his goal was to show Dr. Journey “what normal Americans think.” But he condemned anyone who sent her death threats or hateful messages. And, he said, even if he had not posted her email address, “let’s face it, people would have found it.”

Mr. Schmidt has found himself in adversarial roles before.

Over the last year or so, he actively supported Kanye West, the artist now known as Ye, for president — work that he promoted with Nick Fuentes, a Holocaust denier. Mr. Schmidt declined to comment on his political activism or his dealings with Mr. Fuentes.

In his first year at the university, Mr. Schmidt was fired from The Chicago Maroon, the student newspaper, after his editors said that he had repeatedly antagonized another columnist on Instagram, and encouraged others to spam her. Mr. Schmidt said he was simply “calling out a public figure.”

After he was also fired from a conservative campus publication, Mr. Schmidt turned to his own website, College Dissident, which featured articles like “Time to Fight Anti-White Hatred on Campus.”

His activism has helped fuel an industry dedicated to accusing universities of liberal orthodoxy. Websites like Campus Reform and The College Fix have for years trained students to report on campus controversies, hoping that conservative news outlets like Fox News, Breitbart and The Daily Caller will whip out their own stories.

All three publications ended up writing about Dr. Journey’s class.

And after the course catalog said the class was canceled for the winter, Mr. Schmidt celebrated. “This is a huge victory,” he tweeted.

Two weeks after Mr. Schmidt’s first tweets in November about the course, John W. Boyer, then dean of the college, sent an email to a handful of staff and faculty, describing the incident as “cyberbullying,” intended to intimidate the instructor by mobilizing anonymous threats and harassment. The university, he added, would not allow it.

But by February, the university had dismissed Dr. Journey’s complaints. Officials declined to discuss the case, citing privacy concerns, but said that the school had “policies addressing harassment, threats or other misconduct, including cases that involve online communications,” which cover all students.

Dr. Journey was furious. “I don’t want disciplinary action against this student just for a sense of justice for me personally,” she told The Times. “By condoning cyberabuse, there’s no deterrent effect.”

In his dismissal, Jeremy W. Inabinet, an associate dean of students, acknowledged that becoming a target of online criticism could be disturbing. His office, he said, would recommend that the college talk with the student.

That discussion did not happen, Mr. Schmidt said.

In March, four days before the course was to begin, he posted again, this time on TikTok, complaining about a December column in The Maroon by Dr. Journey and a local news article in November, in which she was quoted as saying, “We can’t let cyberterrorists win.”

In the video, he said, “People have a right to know who’s teaching these classes” and re-shared her photo and email address. Dr. Journey’s inbox was on fire again.

Administrators had already amped up security. They had moved Dr. Journey’s class to a building that required key-card access and did not publicly list the location. Dr. Journey said the university beefed up security patrols.

Officials also took key steps that supporters of academic freedom say many colleges fail to do: They affirmed Dr. Journey’s right to teach the class and did not distance the institution from her.

But Dr. Journey continued to receive a stream of emails, hundreds in total, as well as letters to her home and office. Someone signed her up for a Pornhub newsletter.

Dr. Journey filed another complaint to the university in April, this time also signed by Shannon Lee Dawdy, then the chairwoman of the anthropology department.

“On a campus famously dedicated to academic freedom,” they wrote, “students cannot be allowed to launch public hate campaigns with the intent of intimidating faculty and shutting down the teaching of material that they do not like.”

That complaint, too, was dismissed.

Mary Anne Franks, a University of Miami law professor who studies civil rights and technology, said that universities should pay more attention to the intimidation of faculty members.

Cyberbullying “is much more intentional, vicious and threatening to a person than someone shouting unpleasant things to a person during a talk,” she said, adding that Mr. Schmidt’s behavior “was very much calculated to generate exactly the reaction that it did.”

Professor Stone, who wrote the Chicago statement, agreed that the student’s actions could have a “chilling effect” on speech. But, he asked, who determines the difference between, say, a newspaper reporting on an individual and Mr. Schmidt’s actions? Both can result in hate mail and threats, he said.

The university, as a private institution, could change its policies to say that students, staff and faculty cannot post material that is intended to be intimidating, Professor Stone said.

But such a move — which he does not recommend — would run afoul of the First Amendment if the university were public, and would bring its own complications, he said.

“It’s very hard for either law or institutions to monitor those sorts of things,” he said. “Your administrators may be biased in terms of who they go after, and who they don’t go after.”

And while a strong case could be made that Mr. Schmidt’s intent was to intimidate, Professor Stone said, “Do you really want to get into the business of trying to figure out what the purpose was?”

That explanation can be unsatisfying for students wanting a solution. Watson Lubin, a senior in Dr. Journey’s class, said that he chose the university in part because of its reputation for academic freedom. But over his four years, he said, he has soured on the free-expression rhetoric.

“I’m worried that Daniel Schmidt actually formed something of a precedent here,” he said, “where you can, under the auspices of free speech, more or less intimidate and harass a professor, and sic your incredible following on TikTok and Twitter on them for the purpose of chilling speech.”

A few weeks ago, as his sophomore year closed, Mr. Schmidt posted another TikTok video about the class and complained again about Dr. Journey’s column.

“This is too far,” he said. “Kids in my school, what, they’re partying. They’re having fun. And meanwhile, I got to deal with this.”