Nearly three dozen former employees from Facebook’s early days on Wednesday blasted CEO Mark Zuckerberg’s decision not to act against incendiary posts by US President Donald Trump as “cowardly” and a “betrayal” of company ideals.

The open letter, initially reported on by the New York Times, deepened a crisis facing Facebook’s leadership team, who had to defend their decision at a tense all-hands meeting the day prior following an employee walkout over the issue.

Criticism of Zuckerberg’s hands-off approach to speech by political leaders reached a crescendo last week, after rival social network Twitter began putting warning labels on several Trump tweets that the platform said contained misleading information and glorified violence.

The company we joined valued giving individuals a voice as loud as their government’s — protecting the powerless rather than the powerful

Snapchat likewise took a hard line, booting Trump’s account on Wednesday from a curated “discover” section of its app which promotes fresh content.

The former employees, including a staffer who opened Facebook’s office in Washington, implored Zuckerberg to implement checks on speech by political leaders as it does for other users, including fact-checks and labels on harmful posts.