X Sues Media Matters Over Research on Ads Next to Antisemitic Posts

X, the social media service formerly known as Twitter, sued Media Matters in federal court on Monday after the advocacy organization published research showing that ads on X appeared next to antisemitic content.

A post last week from Elon Musk that endorsed an antisemitic conspiracy theory, which he wrote a day before the Media Matters research was published, kicked off an advertiser exodus, with major brands like IBM, Apple, Warner Bros. Discovery and Sony pausing their spending on the platform.

X has rejected Media Matters’ findings, saying they were not representative of a regular user’s experience on the platform. On Friday, Mr. Musk promised a “thermonuclear lawsuit” against Media Matters and its backers.

The lawsuit, filed in U.S. District Court for the Northern District of Texas, claims that Media Matters tried to damage X’s relationships with advertisers. “Media Matters has manipulated the algorithms governing the user experience on X to bypass safeguards and create images of X’s largest advertisers’ paid posts adjacent to racist, incendiary content, leaving the false impression that these pairings are anything but what they actually are: manufactured, inorganic and extraordinarily rare,” lawyers for X wrote in the complaint.

Media Matters did not immediately respond to a request for comment on the lawsuit. Angelo Carusone, the president of the organization, said on Friday that Mr. Musk had confirmed that ads ran on X alongside pro-Nazi content.

“Far from the free speech advocate he claims to be, Musk is a bully threatening a meritless lawsuit in an attempt to silence reporting that he even confirmed is accurate,” Mr. Carusone said on Friday. Media Matters would prevail in a lawsuit, he added.