“For too long, Facebook and other social media companies have claimed not to be ‘arbiters of the truth’ that appears on their platforms,” he said. “Facebook’s newest move to remove extremists like Alex Jones and Milo Yiannopoulos from the platform is just the latest piece of evidence that this is not the case. The social media companies not only have the right, but an ethical responsibility to remove disinformation and hate speech and those who spread it from their platforms.”

Many of the users barred by Facebook had previously been prohibited on other social media services. Mr. Yiannopoulos, a former Breitbart editor and far-right media personality, was banned from Twitter in 2016 after leading a harassment campaign against the actress Leslie Jones. Laura Loomer, a right-wing provocateur, was barred by Twitter earlier this year for making Islamophobic comments about Representative Ilhan Omar, Democrat of Minnesota.

The others banned by Facebook on Thursday were Paul Joseph Watson, an Infowars contributor, and Paul Nehlen, a white nationalist who ran unsuccessfully for Congress in 2018. Infowars was also booted.

Mr. Watson said in a tweet that he was given no reason for his eviction by Facebook. “I broke none of their rules,” he said. “In an authoritarian society controlled by a handful of Silicon Valley giants, all dissent must be purged.” He also appealed to the president for help, complaining in a tweet that Facebook was “now just banning people for wrongthink,” with “no pretense of enforcing rules.”

Other banned users scrambled to steer their followers to other platforms. Ms. Loomer pointed her Instagram followers to her channel on Telegram, a messaging app. Mr. Yiannopoulos told his Instagram followers to sign up for his email newsletter.

An email to Infowars was not returned. Mr. Farrakhan, Mr. Nehlen and Ms. Loomer could not be reached.

At Facebook, the bans follow an internal discussion about its content policies, said two people with knowledge of the matter, who were not authorized to speak publicly. For the past few months, the company has discussed the policies because they either focused on banning a single account, which was too narrow, or labeling someone a purveyor of hate speech or someone who incited violence, which was overly broad and required removing all associated accounts and the content under review — including those of anyone else who was supporting the same views.