For weeks, Tesla CEO Elon Musk has been spoiling for a legal fight with Vernon Unsworth, the British cave diver who played a key role in rescuing a dozen teenagers and their coach from a flooded cave in Thailand.

After Unsworth criticized the “submarine” Musk built to help with the rescue effort, Musk responded by calling Unsworth a pedophile—without a shred of evidence. Unsworth then threatened to sue Musk for defamation.