Lawyers for Tesla and SpaceX CEO Elon Musk are pushing back against a defamation lawsuit brought by the cave-rescue volunteer Musk called a “pedo guy” on Twitter.

Musk lashed out at Vernon Unsworth on social media last July after both volunteered as part of the rescue of 12 Thai boys and their soccer coach from a flooded cave in Thailand. The caver gave a critical interview to CNN claiming that a submersible tube Musk designed for the rescue was a “PR stunt” prior to Musk’s since-deleted Tweet calling him a “pedo guy.”