Elon Musk uses a rude insult to criticize advertisers for pulling out of X.

Elon Musk attacked brands that pulled their ads from X after endorsing an anti-Semitic conspiracy theory on the social media platform.

Mr Musk apologized for the post at the DealBook Summit in New York on Wednesday, but said the advertisers were trying to “blackmail” him. His message to those brands was simple: “Don’t advertise,” and he used an expletive several times to emphasize his point.

About 200 major advertisers, including Disney, Apple and IBM, stopped spending on X after Mr. Musk agreed with a post accusing Jewish communities of “fomenting hatred against white people, which they claim they want people to stop using against them.” If the freeze continues, it could cost the company up to $75 million this quarter, according to internal documents obtained by The New York Times.

While Musk acknowledged that a prolonged boycott could put X out of business, he suggested that the public would be more likely to blame the brands than him for its collapse.

Mr. Musk mentioned Bob Iger, the CEO of Disney, who said earlier during the event that “the association with that position, and Elon Musk, and X was not necessarily positive for us.”

Mr. Musk said that, in retrospect, he should not have responded to that specific message and “should have written what I meant in more length.”

He added: “I handed a loaded weapon to those who hate me and to those who are anti-Semitic, and for that I am deeply sorry.”

Investment banks holding billions in debt that enabled his takeover of the company last year are unlikely to be happy with Musk’s aggressive stance. Advertising represents the bulk of X’s revenue, and Mr. Musk hired an industry veteran, Linda Yaccarino, to help rebuild ties with major brands. Ms. Yaccarino was in the audience when he made his comments.

Lauren Hirsch reporting contributed.