Musk, who has taken to Twitter in recent weeks to combat his critics, drew criticism this weekend after calling a diver involved in the rescue of a Thai soccer team a “pedo.” The diver, Vern Unsworth, had criticized Musk’s effort to create a small submarine to rescue the soccer team members.

Thai rescuers succeeded in bringing the soccer team to safety without enlisting Musk’s help. Unsworth dismissed it as a PR stunt, telling Musk he could “stick his submarine where it hurts.” Musk then lashed back in a now deleted tweet that seemed to hint, by virtue of the British diver’s residence in Thailand, that he was a pedophile.

Unsworth has said he is considering legal action against Musk, while Tesla investors wasted no time in expressing their concerns about the CEO’s erratic behavior. Tesla slid 2.8% during official market hours Monday, before declining more than 1% in after-hours trading.

In May, Tesla shares suffered a similar decline after another erratic performance by Musk during the company’s most recent earnings call. When analysts asked about capital requirements and reservations for its Model 3 cars, Musk cut them off and chided them for “boring, bonehead questions.”

Over the weekend Musk also fended off reports that he had donated to a political action committee devoted to maintaining Republican control of Congress, saying on Twitter that he routinely donated to both political parties. Those reports are less likely to have rattled investors than an emerging pattern of Musk behaving oddly, particularly with insulting language.

Reports that I am a top donor to GOP are categorically false. I am not a top donor to any political party.

— Elon Musk (@elonmusk) July 15, 2018

One of Tesla’s largest investors said last week that Musk should lay off Twitter and focus on the “peace and execution” of the company’s production goals. That sentiment has only grown stronger now. “This thing is unraveling,” Gordon Johnson, managing director of research firm Vertical Group, told the Washington Post on Monday, referring to Tesla and Musk’s short temper.

Ironically, Musk said in an interview with Bloomberg on Friday that he would try to be less combative on Twitter.

“Generally the view that I’ve had on Twitter is if you’re on Twitter, you’re in like the meme—you’re in meme war land. If you’re on Twitter, you’re in the arena. And so essentially if you attack me, it is therefore OK for me to attack back,” Musk said. “If somebody attacks you on Twitter, should you say nothing? Probably the answer in some cases is yes, I should say nothing. In fact, most of the time I do say nothing. I should probably say nothing more often.”

With Tesla’s market value down by $2 billion in one day, shareholders would be better off if Musk had followed his own advice.