Attorneys for X Corp. and a research organization that studies online hate speech traded arguments in court Thursday after the social media platform sued the non-profit Center for Countering Digital Hate for documenting the increase in hate speech on the site since it was purchased by Elon Musk.

X, formerly known as Twitter, alleges the center’s researchers violated the site’s terms of service by improperly compiling public tweets, and that its subsequent reports on the rise of hate speech cost X millions when advertisers fled.

The center is not the only group that has pointed to the rise of hateful material on X since Musk’s purchase in October 2022. Last November, several big advertisers including IBM, NBCUniversal and its parent company Comcast, said that they stopped advertising on X after a report from the liberal advocacy group Media Matters said their ads were appearing alongside material praising Nazis. It was yet another setback as X tries to win back big brands and their ad dollars, X’s main source of revenue. X has also sued Media Matters.

Later that month, Musk went on an expletive-ridden rant in response to advertisers that halted spending on X in response to antisemitic and other hateful material, saying they are are engaging in “blackmail” and, using a profanity, essentially told them to go away.

Thursday’s hearing was called after the center filed a motion to dismiss X’s lawsuit. Breyer said he will take the motion under consideration.

Nevertheless, the billionaire has at times proven sensitive about critical speech directed at him or his companies. Two years ago he suspended the accounts of several journalists who covered his takeover of Twitter.