Elon Musk is asking a judge to throw out a lawsuit against him from a British diver he called a paedophile on Twitter.
The tech billionaire has argued that his comment was part of nothing more than a "schoolyard spat on social media" that readers didn't take seriously.
Mr Musk's motion to dismiss, filed in court on Wednesday, argues that the "public knew from the outset that Musk's insults were not intended to be statements of fact".
The Tesla chief executive used the US spelling "pedo" when he insulted Vernon Unsworth in a tweet in July.
The diver had criticised Mr Musk on CNN when he said his efforts to help rescue 12 Thai boys trapped in a flooded cave were "a PR stunt".
Mr Musk and engineers from his SpaceX rocket company had built a small submarine and shipped it to Thailand to help free the young footballers.
The device wasn't used and Mr Unsworth claimed that it wouldn't have worked to free the boys.
He added: "(Mr Musk) can stick his submarine somewhere where it hurts."
Mr Musk hit back but later deleted his tweets about Mr Unsworth and apologised, but the diver announced in September that he was suing the businessman for $57,000 (£43,300).
He tweeted that his words were "spoken in anger" and that the submarine was built out of kindness according to specifications from the dive team leader.
But Mr Musk went on to email a BuzzFeed News reporter on 30 August and suggest he should investigate Mr Unsworth and "stop defending child rapists", according to the lawsuit.
Mr Musk is also said to have written: "He's an old, single white guy from England who's been travelling or living in Thailand for 30 to 40 years."
He added that Mr Unsworth moved to Thailand "for a child bride who was about 12 years old at the time", according to the claim.
The lawsuit continues: "Mr Unsworth is not a paedophile.
"Mr Unsworth has never engaged in an act of paedophilia.
"Mr Unsworth is not a child rapist."
The claim adds that Mr Unsworth has never been married to a minor.
The British diver lives in Thailand with his "significant other," a 40-year-old woman, and started visiting Thailand in 2011 to explore and map caves, the lawsuit states.
Mr Musk's motion to dismiss argues that the email to BuzzFeed was supposed to be off the record, but the news outlet reported at the time that its reporters had made no such agreement – a standard practice among journalists before publishing anything without attribution.
His attorneys wrote: "While many readers criticised Musk for lodging what they understood to be groundless accusations, not a single reader seemed to construe Musk's statements literally."
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The lawyers argue in Mr Musk's filing: "Here, the reasonable reader would not have believed that Musk – without having ever met Unsworth, in the midst of a schoolyard spat on social media, and from 8,000 miles afar – was conveying that he was in possession of private knowledge that Unsworth was sexually attracted to children or engaged in sex acts with children."
The attorneys add that the billionaire's statements were simply "imaginative attacks", and even if they were offensive, such insults are protected by the First Amendment.