Reddit has banned a forum for White nationalists from its social news website, citing the company’s rules against posting personal information and online harassment.

Reddit spokeswoman Anna Soellner said in a statement that the company banned its “r/altright” forum on Wednesday for repeated violations of its content rules. Soellner said Reddit users can be banned for posting personal information, but her statement doesn’t cite any examples involving the banned forum.

Thousands of users subscribed to the forum named for the “alt-right” fringe movement, which has been described as an offshoot of conservatism mixing racism, White nationalism and populism. Other sites, including 4chan.org, have been popular forums for the movement’s followers, who rallied around President Donald Trump’s campaign.

Reddit founder Alexis Ohanian posted an open letter Monday in which he criticized Trump’s recent executive order restricting immigration from seven countries, calling it “deeply un-American.”

“Our platform, like our country, thrives the more people and communities we have within it. Reddit, Inc. will continue to welcome all citizens of the world to our digital community and our office,” he wrote.

Reddit has offices in San Francisco, Los Angeles and New York City. The platform calls itself “the front page of the internet” and has millions of users. Another subreddit – “r/the-donald” – became a popular forum for Trump supporters during the presidential campaign.

Last year, Twitter suspended social media accounts belonging to several prominent members of the “alt-right” movement, including White nationalist Richard Spencer, who coined the term nearly a decade ago. The social media forum said it suspended five of Spencer’s accounts in November for violating a rule against creating multiple accounts with overlapping uses. But the company allowed him to reactivate one of them less than a month later.

Heidi Beirich, head of the Intelligence Project at the Southern Poverty Law Center, said Reddit forums used to be a “cesspool of hate.”

“Until about a year ago, Reddit was just a free for all. There were no rules,” she said. “It got to be too much even for Reddit.”