The person making the claim bears the burden of proving it. Merely failing to agree doesn't shift the burden of pros to the questioner.

What? It's not being described a theorem (the technical term for a mathematical proposition for which there is a proof). It's an experienced cryptographer saying that a certain operation should be more conservatively designed than it is. He makes arguments that fall short of proof but are the best we can hope for, given the current state of knowledge.

As for the NSA, yes, he documents what is happening pretty well, though it's done through above board channels rather than envelopes full of cash. He quotes an NSA person as saying hybrid protocols are unlikely to receive approval for use in government systems. That is, "if you want the government to buy your stuff ($$$$$), it better not implement hybrid". Similar to Dual_EC_DRBG.