An A.I.-generated smear video falsely accusing an Argentine journalist of incest has been circulating widely online — and the country’s president is mocking the victim.

President Javier Milei, an avid user of X, took to the social media platform furiously over the weekend, posting at least 65 messages that targeted the journalist, Julia Mengolini, a radio host critical who has been critical of his government.

Mr. Milei furiously tweeted and retweeted as supporters openly mocked Ms. Mengolini for the fake video that purported to show her having sexual relations with her brother.

Mr. Milei’s barrage marked one of the most extreme episodes in a pattern of escalating attacks against journalists by the right-wing libertarian president and his allies. Experts say Mr. Milei’s rhetoric, often laced with misogynistic insults, sexually charged innuendo and disinformation, is eroding press freedom and raising the risk of real-world violence.

Mr. Milei has even coined a slogan, “We don’t hate journalists enough,” echoing language popular among supporters of President Trump, whom the Argentine president likes to fashion himself after and who also routinely denigrates and mocks the news media.

While Mr. Milei never actually shared the A.I. video himself, he made clear he considered the campaign against Ms. Mengolini justified retribution.