The letter, which was published by The Guardian and written by Leonard Pozner and Veronique De La Rosa, parents of Noah Pozner, a Sandy Hook shooting victim, wrote that they were targeted by “conspiracy groups and anti-government provocateurs” that used Facebook to call the shooting of 20 children “a hoax.” Those people called the children “crisis actors,” according to the parents. And Pozner and De La Rosa charged Facebook with protecting those comments.

“Our families are in danger as a direct result of the hundreds of thousands of people who see and believe the lies and hate speech, which you have decided should be protected,” the parents wrote to Zuckerberg. “What makes the entire situation all the more horrific is that we have had to wage an almost inconceivable battle with Facebook to provide us with the most basic of protections to remove the most offensive and incendiary content.”

Zuckerberg has come under fire for quite some time over the state of his social network. The site has been accused of acting as a platform for fake news and, like other social networks, continues to face the wrath of harassment. Zuckerberg has said that his company will work hard to battle disinformation on Facebook, but faces a problem in deciding when to take content down.

Earlier this month, Zuckerberg said that he finds Holocaust deniers “deeply offensive” in an interview with Recode. But he added that he didn’t think Facebook should take down deniers’ content.

“I think there are things that different people get wrong—I don’t think that they’re intentionally getting it wrong,” he said. “It’s hard to impugn intent and to understand the intent.”

The parents acknowledged that Zuckerberg said he wanted to move more quickly to take down conspiracy theories like Sandy Hook denial, but they argued it’s not enough. They also suggested Zuckerberg “treat victims of mass shootings and other tragedies as a protected group.” Those in the protected group should also have easy access to Facebook staff who can immediately remove offending content.

“Our son Noah no longer has a voice, nor will he ever get to live out his life. His absence is felt every day,” they wrote. “But we are unable to properly grieve for our baby or move on with our lives because you, arguably the most powerful man on the planet, have deemed that the attacks on us are immaterial, that providing assistance in removing threats is too cumbersome, and that our lives are less important than providing a safe haven for hate.”

Facebook did not immediately respond to a Fortune request for comment.