"Put them back NOW!" the president wrote around 1 a.m. ET, in a message directed to the social networking giant.
Facebook's move against the group reportedly came Saturday, without warning, just three days before Tuesday's presidential election -- and amid concerns that conservative voices are increasingly being blocked on social media.
“People are really, really mad,” Priscilla Confrey, co-director of the group, told NJ.com. “When you have that many people and they’re shut down, they feel silenced.”
Facebook had flagged a couple of posts in recent weeks, including some related to the coronavirus, for being problematic, Confrey told NJ.com -- but she said she always deletes any posts that Facebook marks.
She said she has repeatedly reached out to Facebook to try to understand why the group was shut down.
“Three days before Election Day? That is absolutely appalling," she said.
"I just think these companies, these social media groups, have too much power. They offer to you to open up a group on their social media platform, and you could have 30,000 members, and they shut it down without telling you anything," she added.
Confrey told NJ.com she has contacted lawmakers about the issue. In the interim, she added, the group has started a new Facebook identity.
Facebook did not immediately respond to Fox News' after-hours request for comment.