X (formerly Twitter) owner threatened to file a "thermonuclear lawsuit" against media watchdog Media Matters after several major companies halted advertisements on the platform.
Musk said he would go after the group's "board, their donors, their network of dark money, all of them" once US courts open on Monday.
Media Matters previously published a report detailing company advertisements appearing next to pro-Nazi and anti-Semitic posts on X.
Apple, Disney, IBM, Lions Gate, NBC Universal, Paramount Global, and Warner Bros. Discovery since then announced to temporarily pause running ads on X.
The billionaire, in response, lashed out at the companies being "the greatest oppressors of your right to free speech."
In a blog post, X disputed Media Matters' claims that "completely misrepresented the real user experience" on the social media platform.
Media Matters president Angelo Carusone countered, calling Musk a "bully" that "threatens meritless lawsuits" to stifle reports.
Pro-Nazi and Anti-Semitic Content on X
Musk himself has been under fire over the past weeks for promoting conspiracy theories against Jews on his social network.
The White House even condemned Musk for his "abhorrent promotion" of antisemitism and racism on social media.
The Center for Countering Digital Hate, another group Musk sued earlier, noted that 98% of the 200 posts were flagged to have racist, anti-Semitic, homophobic, or misogynistic connotations.
Musk currently has 163.3 million followers and have been known to boost his own posts on users' feed.
Several Tesla investors, another company owned by Musk, are "frustrated and dismayed" by the billionaire's recent attitude on social media.
X Revenue on Downtrend
The platform has been in decline over previous ads exodus since Musk took over the social network, plunging 50% down with a heavy debt load.
The billionaire hired NBC executive Linda Yaccarino to persuade companies back to no avail. Advertising revenues dropped 60% in September.
Even web traffic was down 7% throughout the first nine months of 2023.
Musk bought the platform, then Twitter, last year for $44 billion with $33.5 billion in equity.
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