If I were to put forth into print, claims against others by an alleged Navy Seal, you can bet I'd PRESS THE ISSUE by asking for the name under which he was Navy Seal.
Even a bank won't take your word for it whomever you "claim to be" when you want to open an account....much less withdraw funds.
I'd think a JOURNALIST, especially writing a defamatory piece and whose reputation, therefore, is at stake (if that's of any concern, of course), would DEMAND PROOF & CREDENTIALS, etc., JUST LIKE A BANK.