In a lengthy interview about Facebook’s policies last week, Mark Zuckerberg used Holocaust Denial as an example of a kind of speech that Facebook tolerates. What Zuckerberg said set off a firestorm of reaction, but was complex and ambiguous in ways that commentators seemed not to grasp. When sister Randi Zuckerberg weighed in to defend her brother, however, she said one thing that was unambiguous: she wants Holocaust Denial to be illegal in the United States.