When Mark Zuckerberg graduated from my high school, he took some ideas with him. Every year, the school published floppy little paperback books, filled up with photos of all the school's students. With all those faces and names and other information — so many people to meet, so much to learn about them — it's hardly a surprise that we looked at the thing all the time. We called it the face book. When Mr. Zuckerberg started his company, so did he.

Mr. Zuckerberg also took, apparently, something else: the school's philosophy about how to operate in a world where people disagree but want to learn from each other. Instead of using lectures and desks, the school teaches most of its classes around seminar tables, big hand-crafted ones that make you feel more civilized just by looking at them.

If you want to understand why he’s defending the rights of people to deny the Holocaust on his now sprawling Facebook platform, consider those tables. Unfortunately, he's turned a truly inspiring teaching system on its head, using it to give wide berth to bullies.

First, take a step back. The school I'm referring to, no surprise to those who follow Mr. Zuckerberg's biography, is Phillips Exeter Academy, the boarding school in New Hampshire.

And those tables? The idea behind the tables is that there is no “behind the tables.” Literally. The alum who thought up the system, a benefactor named Edward Harkness, was shy. He thought it would be easier for students to learn if everyone was right there, circled together, with nowhere to hide. The system has evolved and turned from an innovation meant to encourage kids to come out of their shells into something broader. According to the school, the Harkness system encourages "collaboration" and "respect" that you honor "even when you don't agree." And it's not just for the classroom. "It’s a way of life."

I think that the Harkness system is what Mark Zuckerberg has in mind when he thinks of Facebook. He wants the whole world to sit down calmly and respectfully to discuss, well, everything. As he told the Senate earlier this year, "we consider ourselves to be a platform for all ideas."

Got that? "All ideas."

And that brings us to Mr. Zuckerberg and the Nazis. In an interview covering hate speech on Facebook, Mr. Zuckerberg tried to explain his reasons for not banning more speakers. Apparently forgetting the first rule of debating, he lurched for an analogy with the Holocaust. While noting that he is Jewish and that he finds Holocaust denial to be "offensive," he also said that "I don't think that they're intentionally getting it wrong." Why? Because "It’s hard to impugn intent and to understand the intent."

The next day, he claimed that he "didn't intend to defend the intent" of Holocaust deniers. But at the same time, "our goal with fake news is not to prevent anyone from saying something untrue."

There's a problem here, and it's an obvious one. There's no debating with Nazis. They are simply wrong, to put it mildly. Engaging them makes them seem legitimate. That's all the more so for people who deny the truth, which is the core of denying the Holocaust. If you give those people a platform, you give them a victory. The Harkness system doesn't apply to Nazis.

Even Exeter knows that the world isn’t a leafy New England prep school. In fact, that lesson is coded deep in the school's DNA. When he started it, the school's founder, a man named John Phillips, wrote down his hopes and goals — and a warning: "Goodness without knowledge is weak and feeble, yet knowledge without goodness is dangerous."

The Harkness system, with its goals of exchanging information, is a good thing. But goodness isn't enough. It needs knowledge, which Holocaust deniers spit at. And Mr. Zuckerberg's own knowledge — his absolute certainty that more sharing is always better — will hurt people when that sharing lacks the limit of goodness. Facebook, and all of us who use it, could use some more knowledge and some more goodness right about now. That's the high school lesson Mr. Zuckerberg still needs to learn.

Evan P. Schultz lives in Washington, D.C. He can be reached at evanschultz (at) outlook.com.