More than 70 rights groups sent a letter to Facebook this week asking the site to clarify its content removal policies, especially regarding the social media giant’s compliance with government requests.

“News is not just getting shared on Facebook: it’s getting broken there,” the letter reads. “When the most vulnerable members of society turn to your platform to document and share experiences of injustice, Facebook is morally obligated to protect that speech.”

Late last week, Reuters reported that a board of at least five senior Facebook officials guides the site’s content policy and even makes case-by-case judgment calls. The letter from rights groups questioned specific instances of censorship on the site, including deleted videos of police violence, the temporarily suspended accounts of two Palestinian journalists and the site’s censorship of an iconic photo from the Vietnam War.

For its part, Facebook has promised to allow more controversial content to live on the site, and has made changes to its policies as a result of the Vietnam War picture censorship controversy in particular.

“We have made a number of policy changes after The Terror of War photo. We have improved our escalation process to ensure that controversial stories and images get surfaced more quickly,” Patrick Walker, Facebook’s director of media partnership for Europe, Middle East and Africa, told a meeting of journalists in Norway.

However, the advocacy groups that wrote the letter to Facebook CEO Mark Zuckerberg are still demanding that the site make its content removal policies more transparent to the public.