It set off nonsense alarms in my head, though I don't have first-hand experience - but I had some ideas on how it could be disproven. I went to archive.org and found a book about fish preparation from 1977. Searching for "sashimi" (raw fish sushi) shows several results, including an entire section about it. This tweeter is full of shit.
https://archive.org/details/encyclopediaoffi0000mccl/page/28...