Yale University has been plunged into campus-wide debate and protest over issues of racial sensitivity and free speech so tense it's turning into a national news story, and it all began with two emails about Halloween costumes.

On October 28, a university committee on intercultural affairs sent a campus-wide email urging students to reconsider Halloween costumes that might be racially insensitive. In response a few days later, a lecturer in early childhood development sent an email to the few hundred students in her residential college questioning whether the first email had been necessary and worrying that universities had become "places of censure and prohibition."

Within a week's time, the two emails had led to protests, dramatic confrontations between students and faculty members, and a statement from the university's president that he was "deeply troubled" by students' concerns.

The dispute that started it all might seem trivial. But the uproar is tapping into deeper issues of racism and free speech at the Ivy League university, issues similar to those faced by many American colleges that have come to the forefront this year.

Here's what happened and why it's become such a controversy at Yale and nationally.

How dueling emails about Halloween costumes led to protests at Yale

Every year, without fail, some college students somewhere take Halloween as an opportunity to wear something breathtakingly offensive, including students at Yale who wore blackface in 2007. So, this year, Yale's Intercultural Affairs Committee sent an email urging students to consider whether their "funny" costumes might not be so funny:

Halloween is also unfortunately a time when the normal thoughtfulness and sensitivity of most Yale students can sometimes be forgotten and some poor decisions can be made including wearing feathered headdresses, turbans, wearing ‘war paint’ or modifying skin tone or wearing blackface or redface. These same issues and examples of cultural appropriation and/or misrepresentation are increasingly surfacing with representations of Asians and Latinos.

Such emails are becoming an annual ritual on some campuses. The University of Colorado, the University of Minnesota, and Ohio University all urged their students to wear culturally sensitive costumes in 2013. One of the administrators who signed the Yale email, Burgwell Howard, sent an almost identical note to Northwestern students in 2010, the year after a blackface scandal at that university.

Erika Christakis, a lecturer at Yale in early childhood education, objected to all this. She sent an email to the few hundred students in Silliman College, one of Yale's 12 residential colleges, saying she applauded the goal but questioned whether the email was really necessary.

"I don’t, actually, trust myself to foist my Halloweenish standards and motives on others," she wrote, adding:

I wonder, and I am not trying to be provocative: Is there no room anymore for a child or young person to be a little bit obnoxious… a little bit inappropriate or provocative or, yes, offensive? American universities were once a safe space not only for maturation but also for a certain regressive, or even transgressive, experience; increasingly, it seems, they have become places of censure and prohibition.

She also passed along a message from her husband, Nicholas Christakis, a Yale professor of psychology and Silliman College's master, saying that rather than having the university tell students what to wear and not wear, students should deal with it themselves.

Nicholas says, if you don’t like a costume someone is wearing, look away, or tell them you are offended. Talk to each other. Free speech and the ability to tolerate offence are the hallmarks of a free and open society.

The email infuriated a number of students who saw it as downplaying important racial sensitivity issues. More than 740 Yale students signed an open letter criticizing Christakis's email for minimizing the concerns of students of color. On Thursday, some were reportedly drafting a letter calling for both Christakises to resign as masters of Silliman College.

Nicholas Christakis apologized Friday, though saying he thought his wife's email was well-intentioned: "We understand that it was hurtful to you, and we are truly sorry," he wrote in an email to Silliman students, according to the Yale Daily News. "We understand that many students feel voiceless in diverse ways and we want you to know that we hear you and we will support you."

Colleges are grappling with how to deal with students' requests for greater sensitivity

The Christakises, as masters of a residential college, play a dual role. They're not just faculty members, but are also in charge of students' physical and mental well-being while they're living in the dorms, including living and eating meals with them. Yale presents the residential colleges as intimate, welcoming communities within a larger university.

So the reaction to Christakis's letter was sharper than it might have been if she were just a faculty member who was less involved with students' lives outside the classroom.

"I don’t want to debate. I want to talk about my pain."

"The Silliman Master’s role is not only to provide intellectual stimulation, but also to make Silliman a safe space that all students can come home to," Jencey Paz, a Yale student, wrote in an op-ed for the Yale Herald. "His responsibility is to make it a place … where you can feel free to talk with them about your pain without worrying that the conversation will turn into an argument every single time."

One line from Paz's op-ed stood out: "I don’t want to debate. I want to talk about my pain." This line drew widespread criticism online, and the Yale Herald later took the op-ed offline.

Yale's controversy tapped into a national debate on college culture

The "I don't want to debate" line spoke to a growing trend worrying some observers of higher education, beyond just Yale: In the balance between sensitivity versus critical thinking and academic freedom, students are increasingly emphasizing the former over the latter.

On college campuses around the country, students, particularly students of color, are forcing white students and administrators to confront the pernicious effects of racial bias.

At the same time, students are demanding that colleges be more sensitive to their mental health and well-being. They're feeling empowered to make requests that professors sometimes feel interfere with their long-cherished right to research freely and to speak their mind in public.

The question facing campuses, then, is how to weigh those issues of sensitivity and mental health against sometimes-competing values of free speech and academic freedom.

Students have called for graduation speakers who have done things they consider offensive to be disinvited from commencement. Some have requested "trigger warnings" for material on syllabuses that could exacerbate mental health issues. At Northwestern University, a professor who wrote an essay about a dispute involving a professor accused of sexual assault ended up facing a Title IX complaint due to her comments about the students involved.

Even President Obama weighed in on the debate in September, criticizing college students who want to be "coddled." "Anybody who comes to speak to you and you disagree with, you should have an argument with 'em," he said. "But you shouldn’t silence them by saying, 'You can’t come because I'm too sensitive to hear what you have to say.' That’s not the way we learn."

The debate over how colleges should weigh these requests is complicated by the contradictions at the heart of colleges' relationship with their students. College students are supposed to act like mature adults, but they're subject to the authority of administrators in a way that 18- and 19-year-olds not in college are not. As the price of college has risen, students are increasingly considered paying customers. At the same time, the goal of college is not simply to be happy and comfortable, but to be challenged and grow intellectually.

These are the tensions that Erika Christakis was trying to address in her email. In it, she asked, "What does this debate about Halloween costumes say about our view of young adults, of their strength and judgment?" It's clear that the students in Silliman College want the university to take a more active role in their lives than some faculty would prefer.

This is about much more than just Halloween

All that said, what's happening at Yale isn't only a debate about sensitivity versus free speech. The Halloween email — and other Halloween weekend events that have fed student protests — are tapping into deep and troubling issues of race at Yale.

"To be a student of color on Yale’s campus is to exist in a space that was not created for you," concludes the student open letter responding to Christakis. "From the Eurocentric courses, to the lack of diversity in the faculty, to the names of slave owners and traders that adorn most of the buildings on campus — all are reminders that Yale’s history is one of exclusion."

One of Yale's 12 residential colleges is still named after John C. Calhoun, the virulent racist and secessionist who once defended slavery as a "positive good"; it was given that name in 1933, and only this summer, after the Charleston shootings, did the university seriously begin to consider changing it.

At Yale, just 7 percent of students are black. Black faculty are even scarcer, and their share of total faculty positions has been virtually unchanged since the 1970s.

During Halloween weekend, Yale's Sigma Alpha Epsilon (SAE) fraternity allegedly turned away a black woman student, saying the party was for "white girls only," an incident that the fraternity disputes but at least three students described to Susan Svrluga of the Washington Post.

Students who gathered to write messages in support of black women on Yale's sidewalks on Thursday ended up confronting the college's first black dean, Jonathan Holloway, pleading with him to speak out about reports of racism at SAE as well as about the email controversy.

According to Isaac Stanley-Becker, a Yale student who wrote about the confrontation for the Washington Post, the students said they felt betrayed by Holloway, a professor of African-American history who they felt has not done enough for black students on Yale's campus.

The emotional outpouring seems to have taken administrators by surprise — and shaken them.

Holloway wrote an email to campus Thursday, saying he was moved by students' "profound pain."

"Let me be unambiguous, I am fully in support" of the email urging students to avoid offensive costumes, he wrote: "We need always to be dedicated to fashioning a community that is mindful of the many traditions that make us who we are."

Yale's president, Peter Salovey, met with a group of about 50 students, most of them students of color, on Thursday night, for a conversation Salovey says left him "deeply troubled" that "some students find life on our campus profoundly difficult."

"I do not want anyone in our community to feel alone, disrespected, or unsafe," he wrote. "We must all work together to assure that no one does."