Advertisers have been skittish about X since Mr. Musk bought the social media service last fall and said he wanted more free speech and would loosen content moderation rules. That meant the platform could theoretically place brands’ ads next to posts with offensive or hateful speech.
Many companies, including General Motors and Volkswagen, have balked at various points over the past year at having their promotions appear alongside a heavily documented surge in hate speech, misinformation and foreign propaganda on X. In April, Mr. Musk said nearly all advertisers had returned, without indicating whether they were spending at the same levels; he later noted that ad revenue had fallen 50 percent.
Mr. Musk also swung from threatening any advertisers that dared to pause their spending with a “thermonuclear name & shame” to wooing them by choosing Ms. Yaccarino, a former top ad executive at NBCUniversal, to replace him as chief executive. He picked public fights with major spenders like Apple and churned through sales executives given the task of maintaining relationships in the advertising industry. Top advertising companies, such as IPG, urged their clients to step back from X.
Advertising had long been about 90 percent of Twitter’s revenue before Mr. Musk bought the company. Last month, X told employees that the company was valued at $19 billion. That was down from the $44 billion that Mr. Musk paid.
The heightened sensitivity around antisemitism, Mr. Musk’s penchant for public squabbling and general fatigue after months of fuss over X left many advertising professionals hesitant to weigh in on Friday.
“Clients have always had to make decisions about content they will or will not be associated with,” Renee Miller, the founder of the Miller Group advertising agency in Los Angeles, said in an email. “We generally counsel our clients to not take an openly public political stand.”
IBM, which cut off about $1 million in advertising spending that it had committed to X for the rest of the year, said on Thursday that it had “zero tolerance for hate speech and discrimination.” The tech company acted after a report this week from Media Matters for America, a left-wing advocacy group, which said ads from companies including Apple and IBM were appearing on X next to posts supporting white nationalism and Nazism.
Mr. Musk posted late Thursday that “Media Matters is an evil organization.”
Angelo Carusone, president and chief executive of Media Matters, said Mr. Musk’s “calling us evil” for pointing out what was on X was “not dissimilar from any right-wing account who we highlight.”
He added that X was “not just going to just lose money with Apple, but also the cornerstone of their strategy to woo back advertisers.”
Kate Conger contributed reporting.