Elon Musk’s social media platform, recently rebranded as X from its original name, Twitter, has issued a legal warning to a group of independent researchers. This group had presented findings of an upsurge in hate speech on the platform since Musk took ownership last year.

A lawyer representing the platform wrote a stern letter to the Center for Countering Digital Hate (CCDH) on July 20. The letter outlined a possible legal battle over the nonprofit’s investigation into hate speech and content moderation on the platform. The social media company argues that CCDH’s research publications seem designed “to harm Twitter’s business by driving advertisers away from the platform with incendiary claims.”

Musk, known for his strong stance on absolute free speech, has been inviting controversial figures such as white supremacists and election deniers back onto his platform. However, the mogul has been known to be rather thin-skinned when it comes to criticism directed at him or his enterprises.

The CCDH, a nonprofit organization with offices in both the U.S. and U.K., regularly releases reports on instances of hate speech, extremism, and harmful behavior across social media platforms like X, TikTok, and Facebook.

This organization has put out several reports criticizing Musk’s leadership, highlighting a spike in anti-LGBTQ hate speech as well as misinformation related to climate change since he took over. X’s attorney pinpointed one report from June in their letter, which indicated the platform’s failure to eliminate neo-Nazi and anti-LGBTQ content from verified users, which is against platform rules.

In his letter, lawyer Alex Spiro questioned the researchers’ credibility and accused the CCDH of maliciously attempting to tarnish X’s reputation. The letter even insinuated, without any proof, that CCDH was funded by some of X’s rivals. This is despite the fact that the CCDH has also released critical reports about other major platforms like TikTok and Facebook.

“CCDH aims to damage Twitter’s business by pushing advertisers away from the platform with explosive claims,” Spiro wrote, referring to the platform by its previous name.

The founder and CEO of CCDH, Imran Ahmed, spoke to the Associated Press (AP) on Monday. He expressed that his group has never received such a response from any tech company before, despite their extensive history of analyzing the link between social media, hate speech, and extremism. Ahmed noted that usually, those criticized by the center respond by either defending their actions or committing to address any highlighted issues.

Ahmed voiced his concern that X’s reaction to their work might scare off other researchers from studying the platform. He also feared that other sectors might adopt this kind of approach.

“This is an unprecedented escalation by a social media company against independent researchers. Elon Musk has just declared open war,” Ahmed told the Associated Press. “If Musk succeeds in silencing us, other researchers will be next in line.”

Efforts to reach Spiro and X for comments on Monday proved unsuccessful.

This is not the first instance of Musk retaliating against his detractors. Last year, he suspended several journalists’ accounts after they reported on his acquisition of Twitter. He also suspended a user who used publicly available flight data to track Musk’s private jet, despite initially promising to keep the user on the platform. Musk cited personal safety concerns as the reason for his change of heart and also threatened legal action before reinstating the user under specific conditions.

Musk initially assured that he would permit any speech on his platform that wasn’t illegal. “I hope that even my worst critics remain on Twitter, because that is what free speech means,” Musk stated in a tweet last year.

X’s recent lawsuit threat has elicited concern from U.S. Representative Adam Schiff, a Democrat from California. Schiff argued that the billionaire was attempting to intimidate a nonprofit group that’s working to hold a potent social media platform accountable by using the threat of legal action.

“Instead of attacking them, he should be addressing the increasingly disturbing content on Twitter,” Schiff commented in a statement.