The head of the Anti-Defamation League said the spread of antisemitism and hate on X, formerly known as Twitter, was deeply troubling, amid owner Elon Musks threat to sue the group over such claims this week.

Jonathan Greenblatt, the CEO and national director of the ADL, spoke about Musks warning on Tuesday, saying he wouldnt comment on frivolous lawsuits but that there was an unequivocal surge in hate on social media. The group said in May that Xs decision to reinstate previously banned accounts had helped foster social spaces where Twitter users connected through shared antisemitism and other hate.

There is a problem across all social media services. Weve talked about it before. Ive talked about it on this network. Ive talked about it with Elon Musk, Greenblatt told CNN s Abby Phillip. Literally, anti-Jewish acts have reached historic levels in the United States. The highest number weve seen in 40-some-odd years of tracking it.

The truth is, is that, Im concerned about whats happening in this country, Greenblatt added. Im deeply worried about the antisemitism affecting American Jews. Frivolous lawsuits, wild claims, I cant respond to them. Ive got to do my job, which is to fight hate.

His comments came after Musk said X, formerly known as Twitter, had no choice but to file a defamation lawsuit against the group over the companys loss in advertising revenue. Musk claimed the tech giants income from ad dollars in the U.S. had dropped 60% and that the ADL seems to be responsible for most of our revenue loss.

Giving them maximum benefit of the doubt, I dont see any scenario where theyre responsible for less than 10% of the value destruction, so ~$4 billion, Musk wrote at the time.

X has not yet actually sued the group, but filed a separate case against the Center for Countering Digital Hate in August, saying the nonprofit had spread false claims about hate speech on the platform.

Greenblatt went on to say that he supported the First Amendment, adding speech you dont like is the price of free speech.

The question is, are you elevating it? Are you expanding it? Are you making it easy to see for children and other people? Are you finding ways to de-amplify it and to tamp it down? Greenblatt asked. Weve seen an increase in kind of QAnon hashtags. Weve seen a lot of notorious antisemites re-platformed. And this weekend alone was exhibit A in ugly, grotesque, poisonous antisemitism.

So, Ive got to look at what we see, he said. And what we see is deeply troubling.