If he can't prove it (since you can't prove a negative) he shouldn't be claiming that he knows that it hasn't happened and everyone is faking it; worse, he claims to know it happened only twice in history; and worse that his master was the second one other than Buddha himself. He's the one making wild positive claims here, the burden of proof is upon him to support them with evidence. That's why I don't have to prove anything; I've made no claims at all, why would I have to prove anything?
Don't throw your lot in with anyone making claims they can't back up; but make sure your paying attentions to who's making the claims and whether they're proper non negative claims.
